Fire simulation in Blender

1. Intro: Blender is an amazing tool, and it is giving you access to so many different tools, and one of those tools is fire simulation. Fire simulation is a beautiful tool that will help you to add some awesome smoke and flame into your animations. However, as great as fire simulation is, it can also be a little intimidating for new Blender users to learn. If you are trying to learn how to use fire simulation, this is a class for you. In this class, I will show you how does the fire simulation work, how to set it up, different settings that will give you different appearances for your fire, how to texture your fire, how to set up the effector, and all other things you need to know in order to use fire simulation. So sit back and allow me to show you how to use fire simulation. 2. Flow object: In order to add a fire simulation in blender, simply add a UV sphere. Press Object. Quick effect, and select quick smoke. By doing this, Blender automatically gave us this very simple smoke simulation. Now, before we actually start talking about the details, let's first do a breakdown of how does the fire simulation even works. Whenever you want to add a fire simulation and blender, what you will need are two objects. You will need one object that is going to be the flow and one object that is going to be the domain. If we select this UV sphere, and if we go under the physics, you can see that under the type, it is set as the flow. And what flow objects are is they are the source of fire and smoke in your simulation. All fire and all smoke you will get is going to come from your flow object. Next, what you need is A domain. If we select this cube, you can see that it is set as the domain under the type. And what domain represents is basically the area within which your fire and smoke can function. If we let display, as you can see, smoke is rising into the sky until it reaches the top of this domain, and at that point, it can't go any higher than this. If we move this flow object halfway out of the domain, you can see that only the half that is within the domain is emiting fire is emiting smoke. And if we remove it completely, we are no longer getting any fire at all. So every time you are working with five simulation, make sure that your domain is covering all the areas where your fire and smoke need to go. Since, like I said, they will only be able to exist within the domain. Okay. Now, both the domain and the flow objects have a lot of cool settings that can help you to make beautiful fire simulation. However, in this lesson, we are going to mostly focus on the flow object. First, big problem we have. This flow object is only a meeting smoke, not fire, how to fix that. To fix that, under the flow type, simply switch this from smoke to fire plus smoke Now, as you can see, now this flow object is emitting fire as well. And also you have just fire. This fire is pretty self explanatory. Now, even if you set your flow object to fire, you are still going to get some of the smoke. But still, it is a lot fewer than when we had fire plus smoke. Let's switch this back to fire plus smoke. And next, we need to talk about flow behavior. Flow behavior is going to control how your flow object is adding fire. By default, this is set to inflow. And what inflow is going to do is it is going to cause your flow object to constantly add more fire and smoke into your simulation for every new frame. So every other frame, this flow object is adding more fire and smoke into your simulation. Next, we have the geometry. Now, geometry is going to do something interesting. Let's let this animation play. Okay, as you can see, geometry added some fire, but that fire lasted for a very short period. Why is that? Well, what geometry setting is going to do is it is going to cause your flow object to be filled with fire and smoke. But it is only going to emit fire and smoke for the first frame of your simulation. As soon as you move past that first frame, your flow object will stop emitting fire. This setting is actually really useful if you want to make something like the explosion. But if you want to cause your object to consistently burn, you will need to use the inflow. Now, last setting we have is the outflow. But to explain what outflow does, we will need a new object. So select your domain, make it bigger because we will need more space for this. And also what I recommend you after you finish setting the scale for your domain, press Control A, and select the scale. That is going to reset the scale of your domain. And I found that fire looks a lot lot better when your domain has a reset scale. Now, let's simply add a cube. Move it up. Let's scale it like this. Move it a tiny bit closer. Control A, scale. Now, go to the object properties. Under viewport switch displays to wires for better visibility. Go to physics, enable fluid, switch this to flow, switch flow type to fire plus smoke and switch this flow behavior to outflow. Now, let's see what is going to happen when we play this animation. Okay, as you can see, something strange is happening. Let's let this animation play. Actually, Okay, this is good. Now, watch carefully what is happening here. This fire and smoke rising. They're going up until they get close to this until they get close to this cube. As soon as smoke reaches this cube, it disappears. Now, why is that? You see, guys, flow object What outflow setting does is it is causing your object to behave like a sponge. The second, your fire and smoke. Touch the object that is set that is set as the outflow. The smoke is going to be sucked into that outflow object and it is going to be deleted. So outflow is a really cool setting to use. If you need to quickly get rid of some of the smoke in your simulation, since like I said, as soon as your smoke touches the outflow, it is going to disappear and be cut out of your simulation. Okay. Now, few more things. In case your file simulation stops working, or it is not behaving according to the changes you added in your simulation, there are a few things you can do to fix that. First, what you can do is you can reset your simulation to do that, select your domain. Change any setting in the domain and then change that setting back to how it was previously. Doing so will cause your simulation to be reset, and that should fix your issues. In case this doesn't work, in case your fire still doesn't work properly. If your fire just disappears out of your simulation, another thing you can try is you can also increase the resolution of the fire if for whatever reason, your fire disappeared when you added flow object you can simply increase the resolution of your fire of your domain, and that should also fix your problem. However, guys, keep your resolution relatively low. Don't set your resolution too high. I'm going to set it to 50, and I'm not going to set it any higher than this. I'm going to talk about I'm going to talk about a resolution in the next lesson a tiny bit more. However, all you need to understand for about the resolution for this lesson is that you shouldn't set this too high, keep this at a low value. And if your simulation doesn't work, you can fix that by changing this resolution and then changing it back to how it was previously. And if that still doesn't work, you can increase your resolution. However, once again, do not I repeat, do not set your resolution too high. Now that we explained what outflow setting does, we can actually delete this cube. We don't need it anymore. And now, looks like my simulation is a little glitched. So I'm just going to quickly reset this simulation. Okay, this fixed my problem. Okay, the next setting we have to talk about is these subframes. However, in order to properly explain what subframes do, we need to cause this simulation to be set into the motion. We need to cause this flow object to move around a bit. To do that, press the psychon that is going to enable auto king. Now, press spaceNG and simply move your flow object around and try to move it really, really fast. H. Okay, by enabling out a king, we told Blender to add a keyframe. Every time we make a change in our scene. And as you can see, by doing this, Blender added one keyframe. For every time we move this flow object, let's disable out a king. We won't need it anymore. And now we let this animation play. Now as you can see, our flow object is copying every movement we made with it. However, let's now explain what subframes do. Let's let this animation play. Uh huh. Okay, it is happening here. Now, watch carefully what is going to happen here. Our fire is here, then here, then here, then here. However, the problem is our flow object is not adding fire into our scene consistently. We have one ball of fire here, then here then here, and the next one is all the way here. Why is this happening? Why is our flow object not adding fire consistently? Well, you see, when you have flow object that is moving fast, what can sometimes happen is blender can be a little confused about how should your fire move between frames. And if that happens, what you will get is this broken fire where flow object is adding a new burst of flame for every frame of your simulation. And sub frames are going to help us to fix this. Sub frames are basically going to cause blender to calculate how should our fire move between frames. Let's increase this to a value of five, and let's see how does this look now. Okay, let's go back a tiny bit. Okay, this looks a lot lot better, but we still have a small issue with fire. Let's increase this to eight. Okay, now our fire looks really, really, really good. So basically, the higher you set this value, the more smoother your simulation is going to look. However, guys, do not set this value too high. Why? Because this value is adding pressure to your blender, not much pressure, but that pressure is definitely present. And if you set this value too high, you are going to crush your blender. Simply give this value, simply give subframes value that is going to give you a decent result, but make sure to not set this up too high and you shouldn't have any issues. I'm going to set my sub frames to the value of 12. I believe that is going to give me the best result. And now let's actually move on to the next important setting density and fuel. What do these two settings do? Well, to explain, actually, let's test sub frames before we start talking about density and fuel. Okay, with sub frames, as you can see, we now have nice pretty fire where this flow object is adding fire consistently. However, now let's talk about density and fuel and to talk about them, we need to cause this flow object to now be standing still. So let's select all the key frames and delete them. Now what do density and fuel control. Density and fuel controls, how much fire and smoke you are going to have in your simulation. Let's increase this fuel value to a value of ten, and let's see what is going to happen. Okay, as you can see, now we are having a lot of fire in our simulation. And if we set this to a value of zero, Okay. Now, as you can see, now we are no longer getting any fire, just the smoke. So basically what fuel value controls is how much fire you are going to have in your simulation. Fuel value controls how much fire your flow object is going to add into your scene. And next we have density. Let's set this value to something like ten, and let's actually set fuel to zero because I believe that without fire, the result of density is going to be the most obvious. Now, density does very similar thing like a fuel only for the smoke. What density is going to control is how much smoke you have in your sind blender and how thick that smoke is. The higher you set this value, the more smoke you are going to get, and that smoke is also going to be thicker. And if we set this value to zero, as you can see, we are no longer getting any smoke. And actually, if we give our fuel some value, but keep density at zero. And if we let display, you can see if you just add fire, that fire is going to automatically add some smoke into your simulation, but that smoke is going to be in a very low amount. So what you need to know, density controls how much smoke you have in your sin in blender and how thick that smoke is going to be, and fuel controls how much fire you are going to have in your simulation. Next, we have flow source. With flow source, we need to talk about this thing called surface emission. What surface emission controls is how far from your flow object is fire going to be emitted? If we set this surface emission to a value of seven, filet display, you will see that this fireball is now a lot bigger, since now fire is being emitted further away from your flow object. If you set this surface emission to a value of zero, you will lose all the smoke. But if you give it a low value like 0.1, now you will get this, um ball of fire, but that ball of fire is going to be very, very small since now your fire is being emitted really, really closely to your flow object. This is just one very simple setting to use if you want to control how big your fireball is going to be. Next, we have initial velocity. Now, to best explain what initial velocity does, we will once again need to set this flow object into the motion. So simply pick a new movement pattern for your flow object. And now, let's watch how does this fire behave? Okay. I actually think that smoke is actually getting in a way, a little of our visibility. So let's let this flow type to just fire, and let's see how is our fire behaving? Okay. Now, as you can see, our fire is now moving like a shooting star. It is very, very smooth and it is moving in one straight line. Now, if this is something that you want, then there is nothing wrong with this fire behavior. However, realistic fire doesn't move like this. Realistic fire isn't this smooth. It's random, it's unpredictable, and it's moving in all directions. And to recreate that behavior, you can simply enable initial velocity. And now that we enable this, let's see how is this fire going to behave now? Okay, now this looks a lot lot better. Now our fire is random, it's unpredictable, and it's behaving like a real firewood. So yeah, this is just one very simple tool to use if you want to get a realistic looking fire. With this explained, we can once again delete these key frames. We need to cause our fire to once again be still, and we can also switch the flow type back to smoke. Okay, however, there is one more thing you can do with initial velocity. However, to explain what that one thing is, we need to increase the size of this domain. So select your domain, increase its size, and press Control A to reset the scale. Now, if you look carefully, you can see that here we have X, Y, and Z axis. And under initial velocity, we also have X Y and Z value. Let's see what is going to happen if we give X value, the value of 15 50 or 59. Let's play this. Okay. Now as you can see, now fire is getting pushed into this direction. Basically what initial velocity settings also controls is in which direction the fire is getting emitted from the flow object. The stronger you set this initial velocity, the stronger this effect is going to be. If we switch this to ten, you can see that fire is still getting pushed in this direction, but now no longer with such a force. Also, if we switch this initial velocity to the value of negative 19. Now as you can see, now this fire is also getting emitted, but in the opposite direction, so yeah, this is just one very simple tool you can use if you want to get your fire to be emitted from a specific direction. And with this, we covered pretty much all you need to know about flow objects. In the next lesson, we are going to talk about domain in bit more details. However, before we end this lesson, there is one more friendly advice I would like to give you, and that advice is save, save constantly. Save every time you make some big change in your fire simulation. Why? Because fire simulations, especially the ones that are bigger and more detail, are going to put a lot of pressure on your blender. And if you don't save, what can happen is your blender can crash, and then you will lose all the progress you have made. But if you save, you can be 100% sure no progress will be lost. So simply save your file, save your sin in blender, and also make sure to save every time you make some big change. Okay, with this, we covered everything for the first lesson. See you guys in the next lesson when we will be talking about the domain. 3. Domain settings: Welcome back. In the previous lesson, we were talking about the flow object and how you can use it to get an interesting results for your file simulation. However, we are only halfway done. There is still one more thing we need to discuss. We need to discuss about the domain. The flow objects are useful, but the domain objects also have a lot of cool settings, which we can use to make very good fire simulation. However, to best demonstrate how can Domain help us get a good looking fire simulation? We first need to once again set this Usphere into motion. So once again, enable Ato king and set a new movement pattern for your fire simulation. H. Okay. I believe this is going to be good. Okay. But we have one problem. This domain is way too small. So let's press to scale it up. Actually, let's make it wider a bit as well and taller a little more. Okay, now press Control A to reset it scale. And let's see how is this looking now? Okay, this is looking relatively good. Now, it's good enough for now. Okay. Okay, so let's start talking about the domain. First, under the physics settings of the domain, first, we have the resolution. Now, in the last lesson, I told you not to set resolution too high, and here is why. What resolution controls is what is going to be the quality of your fire simulation. The higher you set this value here, the higher is going to be the quality of your fire simulation. Now, the reason why we needed to keep this resolution low is very simple. You see, guys, the higher you set up your resolution, more pressure is your simulation going to put on your blender. And if you put your Resolution two. Hi. What is going to happen is your blender is going to crash. So this is what I recommend you. While you are setting up your fire simulation, I recommend you to keep your resolution at a relatively low value, and only once you finish setting everything up. Only then give it a higher resolution and give it a higher quality. That way you are going to minimize the risk of blender crashing and minimize the risk that you are going to lose any progress if it does crash. However, even with the resolution being kept at a low value, I still recommend you to constantly save your file. That way you are always going to be sure you are never going to lose anything even if blender does crash. Okay. Next, we have timescale. Now, timescale is pretty self explanatory. It controls how fast your simulation is going to move. The higher value will result in faster moving simulation. The lower value will result in a slower moving simulation. Next up, we have adaptive domain. Now, guys, listen to me very carefully because what I'm going to tell you now is very important. Let's let this animation play. As you can see, our FPS is red and that means that our blender is struggling to keep this animation going in real time. Now, if we go under the output, you can see that FPS is set to 24. The fact that FPS here is red, it means that blender is struggling to run this animation at 24 frames per second. Now, why is that? Well, you see, guys, Blender is right now calculating this entire domain as if it is completely filled with fire and smoke. However, in reality, we only have fire and smoke in the center of this simulation. So there is a lot of unnecessary unnecessary space that is being calculated. And what you can do to solve that problem is under the physics properties of the domain, you can enable adaptive domain. And let's see what is going to happen now. As you can see, this domain is shrinking. It's only wrapping itself around the areas where you actually have fire and smoke. And this is going to be a huge time saver for us, since this is going to lift a lot of pressure off of our PC. Now FPS is still struggling a bit, but still it is a lot better than how it was before. I always recommend you to enable adaptive domain. It is going to cause your blender to run a lot more smoother. However, there is one thing you need to know about adaptive domain. Adaptive domain can cause your domain to shrink but not to expand. If we play this animation, you can see that this domain is only covering the areas where we have fire and smoke, but let's disable the adaptive domain, and let's see what is going to happen if we move domain somewhere where flow object will be right next to its edge. Renable adaptive domain and let this animation play. As you can see, domain is expanding on the right, but it's not expanding on the left. Smoke is acting like it's hitting the wall. Why is this happening? This is happening because adaptive domain can cause your domain to shrink, but it can't cause your domain to expand. That is why smoke is acting like it's hitting a wall. When we set a scale for domain, this is where we put the edge of our domain and fire can't move in this direction anymore than it already does, even with adaptive domain enabled so always make sure that your domain is covering all the areas where your fire and smoke need to go, since domain will only be as big as you set it, adaptive domain will not cause it to grow beyond that. Now, next, we have this dissolve setting. Let's watch this simulation. As you can see, right now in our simulation, we are having a lot of smoke, and that smoke is not fading away. It is just sticking in this simulation and it's not going out. So how are we going to cause this smoke to slowly fade out of our scene? Simply enable this dissolve option. And now if we play this from the start, now you can see our smoke is slowly fading away. But now we actually have the opposite problem. Now our smoke is fading away a little too fast. So to cause our smoke to fade a little slower, open this dissolve value and you can simply increase this time to a higher value. The higher you set this value, the slower the smoke is going to dissolve. Let's see how does this look now? Okay. It looks good. We still have a lot of smoke. Actually, I think we still have a little too much smoke. Let's increase this to 18. Let's see how is this happening now because I don't want my simulation to have too much smoke. Okay, let's decrease this to 15. Okay, this is fast enough. We are getting smoke, but we are not getting too much smoke. And this is a good time to mention. Don't blindly copy every value I put into this simulation. Right now, my goal is to get you to understand what do these settings do and how do they work. However, once you're working with your simulation and blender, don't just blindly copy all values I'm going to put in. Depending on what you want to achieve, you will need to add different settings. If you want a lot of smoke in your simulation, you are going to set this time to a higher value. If you want very little smoke, you will set this to a lower value. And this is true for all other settings I talked about here in this class. So play around, experiment a bit, and don't blindly copy every value I put into this simulation. Okay. Okay. However, guys, even with dsolve enabled and adaptive domain, we still have one more problem we need to discuss. Let's see if we can see it when it is, wait, wait, wait. Let's go back. Okay. Here is one problem. Do you see what is happening here? We have this circle of the cloud. We have this circle of cloud. But what's happening here? I between frames, it gets pretty much cut in half. You see, we have this entire ball of smoke here, and in the next frame, it is getting cut in half here. Now, why did this happen? Why did this smoke get cut in half in one frame? Well, it is because of the adaptive domain and dissolve. You see, adaptive domain and dissolve, these two settings are pretty much at war with each other. Dissolve wants to cause the smoke to slowly fade away over time, but adaptive domain. Adaptive domain is constantly looking for areas where it where it could reduce the size of the domain. So what can happen is if you have a really low amount of smoke in some area, adaptive domain can be like and there's barely any smoke here. It won't be any problem if we cut that smoke out of the simulation. But no, that is a problem because that is not how real smoke behaves. Real smoke doesn't just gets cut out of the existence. It slowly fades away over time. So to get rid of that problem, open adaptive domain setting, and let's increase this threshold to a value of 0.005. Let's see if this problem is going to happen now. Smoke is still getting cut out here, but this does look a lot lot better. So let's decrease this value even more. 005 0005. Let's see how does this look now? Okay. Now we are no longer having this problem and smoke is nicely fading away over time. So yeah, this is good. So, the lower you set this value, the smaller this problem is going to be, simply put any value you think works best for you. Okay, now next what we have is we have the noise. Now, I already told you that resolution controls the quality of your fire. But what you can do to increase your quality even higher is you can also enable the noise. The noise is pretty much going to add a little more realism to your fire. It is going to make it look a little better. Actually, it will make it look a lot better, but it's not going to add too much pressure on your blender. Simply enable noise. Open these noise settings, increase this factor to three, and decrease the strength. Actually, let's leave strength as it is. Let's see how does this look. Noise is a tiny bit too strong here for my taste, let's decrease this strength to 0.5. Still a tiny bit too strong, decrease it to 0.3. Okay, this is going to do. We have now the good noise that is going to add just a little more randomness and a little more realism to your fire. Okay, we are almost done, but there is still one more problem we need to discuss. Let's actually let this animation play from the start. Now, as you can see, our frame rate is still really, really low adaptive domain, it is helping us to speed up the frame rate, but this is still a very big problem. Now, usually in the view port, having low frame rate in the view port is actually not that uncommon. It actually can happen very often. However, when you are working with fire simulation or when you are animating in general, having this slow frame rate can be a little problematic the problem with low frame rate is that as long as this frame rate is this slow, it is impossible to get an accurate sense of how is this fire behaving and moving? The only way to get that sense is by watching this simulation in real time, and how are we going to do that? One word, actually two words, viewport render. We are going to render the viewport of this simulation. Now, how to render the viewport position your viewport somewhere from which you can nicely see your entire simulation. Go to output, switch your frame rate to any frame rate you are using when you are making your animations in blender. I usually use 50 frames per second, but you can use any frame rate that you use when you are animating. Switch this file format to FFVDL under the output, pick a place where you want to save your viewport render. After you picked a place where you want to save your viewport in render, make sure that you save, so that way you won't lose anything if anything crashes, press viewport, select viewport render animation, and now just wait for this viewport to finish rendering. All right, guys, my viewport has just finished rendering. And while I would say this does look good, this simulation still has a few problems. The first problem is that my domain is still way too small, especially on the sides. So I'm going to select the domain, and I'm going to expand it a little more like this. Now I'm going to press Control A to reset it scale. And I also have a feeling that this fireball is moving a tiny bit too fast. So to fix that problem, I'm going to once again delete all the key frames, and I'm going to just redo the movement for this fireball. However, to make sure I won't have to deal with low frame rate, I'm going to select the domain, go under physics properties, and press this icon. Actually, even better, scroll down under the chase and switch this type from replay to all and now, once again, I'm going to pick a new movement pattern for this fire. Okay, under the domain, let's switch this back to replay. Let's reset this domain by changing any setting and then changing it back. Let's turn off adaptive turn off auto king. Now we are going to make a second viewport render. However, guys, one thing I need to warn you about setting up viewport render. When you are making a second viewport render, make sure to give your second viewport, a new name. You need to give it a new name here under the output. Why do you need to do that? Well, it's because if you don't, what can happen is Blender is going to cause your old viewport to get overlapped with the new one and you will lose your old viewport render. It is going to be replaced with the new one. But if you give your new viewport render a new name, you are going to get a new viewport render and you're still going to keep the old one. Once again, nicely position your viewport and viewport render animation. My second viewport has just finished rendering, and I would say that my animation looks really, really good. However, the only problem I still have with it is that I feel that my simulation is still a tiny bit too short. Now, that is only problem for me. If you are watching this tutorial, then don't make simulation that is too long. Keep it a little, keep it relatively short because the main point of this class is to get you to learn how to use fire simulation. So you keep your simulation relatively short, but I'm just going to make mine last a tiny bit longer to make it look more attractive. So once again, I'm going to switch this type to all under the domain. And now I'm going to set the end value 250-500. That is going to double the size or double the length of my animation. And under the timeline, I am going to press Control T. That is going to switch the timeline so that it is no longer showing me the frames. It is showing me the length of this simulation. And now I can see that this animation lasts for about 10 seconds. So once again, I'm going to delete all the keyframes and I'm going to set new keyframes for my view put render. Okay. I believe this is going to be good enough, and now it is time we start giving a finishing touch to this simulation. Let's go to the smoke domain, switch this type back to replay. And now, guys, it is time that we talked about one of the most important settings under the domain. Let's scroll all the way down to the bottom and here we have the chase. Now, what does the chase do? Now, there is one thing you need to understand about fire simulation. Fire simulation is treated as its own separate file. Yes, you do have your sin in blender, which you save every time you press file and save. But blender treats your fire simulation as something that is independent from the rest of your sin in blender. As a result, you need to save your fire simulation separately from the rest of your sine and this chase setting is going to help you do that. Simply press this icon and simply pick a place in your PC where you want to save your fire simulation. After you did this, we have frame start and frame ends. Frames, these settings are pretty self explanatory. They control when is this simulation going to start and when it is going to end? This simulation starts at frame one. But if we set this frame start to a value of 100 and let display, you will see that this simulation will not start. Until we reach the frame hundred, only at that point, this simulation starts. And the same thing happens with this end frame as well. So let's set this frame start value back to one. And since I want my simulation to last until the frame 500, I'm going to set this end value to frame 500 as well. Okay. Next, we need to start discussing the baking. You see, guys, whenever you have fire simulation, you need to bake it, and there are three ways to do it. To. There are actually two ways to do that, and that type is set here. By default, you have this replay option, and this replay is perfect while you are setting up your fire simulation. What replay setting is going to do is it is going to cause your fire simulation to be baked in real time, while this animation is playing in the viewport. For example, if I let this animation play, then this simulation is being baked right now at the same time while this animation is playing, that is actually the main reason why viewport is so slow. Blender is trying to simultaneously bake this simulation and keep the animation going. And like I said, this option is good while you are setting up your sin in blender. However, after everything has been set up, then you need to switch to something else. At that point, you need to switch this type from replay to all and that is going to give you this ball button. By pressing this button, what you are going to do is Blender is going to bake your entire simulation. And yeah, after that, this simulation is going to be more or less finished. However, before we start baking this simulation, there are two things we need to do. Let's scroll up. It's time that we give our simulation a higher resolution now that everything has been set up. I'm going to give my resolution the value of 250. Now, guys, listen to me. Listen to me very closely. This resolution of 250 is very big and it's going to put a lot of pressure on your PC. If you have a weaker PC, I recommend you to give your resolution slightly lower value. Simply pick any value that is high, but at the same time a value that your PC can handle. So don't just blindly copy 250. You don't need to set your resolution this high to get the best possible result. Simply pick any resolution value that is good and that can be handled easily by your PC. So yeah, after you set up your resolution, we are going to save our file. And before we actually start baking this simulation, there is one more thing I would like to set up. Right now, this ov sphere is burning constantly, but what I want, I want my fireball to slowly fade into existence and then to slowly fade out. So to do that, this is what I'm going to do. Actually, for best demonstration, let's once again lower the value of your resolution and switch this type back to replay. I'm not sure did I show you this setting in the last tutorial. Do you see this use flow setting under the flow object? This is basically an on off setting for your flow object. As long as this setting is enabled, your flow object is going to emit fire. So if we disable it, as you can see, we no longer have any fire in our simulation. But if we enable it, you can see fire is coming right back. So what I'm going to do, I'm going to disable these settings. I'm going to wait till the frame where this flow object starts to move, and that is this frame here. Now I'm going to press this dot. This is going to add a key frame to this value. Move one frame forward, re enable use flow, press this dot. To add a key frame again. And now, now that we have set this up, our flow object will turn itself on when we reach the frame to 25, but this is still not good. This fire still just pops into existence. I want this fire to slowly grow, so to do that, let's actually go to the frame, frame, frame, frame. Frame 800, why not? Now, I don't want my simulation to have too much smoke in it. I'm going to send density value to value of 0.5, and I also want my fireball to be big. I'm going to set this fuel value to two. Next, I'm going to press these two dots that are next to these two values, and then I'm going to go back to the frame 26 when our use node setting is enabled. Now switch both of these values back to zero. Press these two values again. Let's reset our simulation to make sure everything works properly. If we play this animation now, what you can see is that now our fireball is slowly appearing into our scene and it is slowly growing. But we also want to do this for the end of the simulation as well. Let's go to the frame 400 close to the end of this simulation. Actually, let's go here slightly more back. Press these two dots for density and fuel value. Move here close to the end of your simulation, set both of these values to zero, press these two dots to add new keyframes, add a keyframe for use flow value, move one frame forward, turn it off, press keyframe again. Now when we play this animation, what is going to happen is that our fireball is going to slowly grow and it is slowly going to shrink and disappear around the end of this animation. So now that we have set everything up, select your domain, increase value, increase resolution back to a higher value. Make sure to save your file. When you are getting ready to bake your simulation, always save your file before you start baking. That way you are going to be 100% sure you won't lose anything even if blender crashes. Scroll down, enable this easy zoomable option. Press switch this type to all, press bake all. And now let's simply wait for this simulation to finish baking. Yeah, my simulation has very high resolution, so this is going to take a while, so Let's just wait for this to finish baking. My bake has just finished, and I also rendered my viewport, and I think this looks really, really good. Now, there is only one thing I would like to change about my viewport simulation, about my fire simulation. And that is, I would like my fireball to be a tiny bit bigger. So what I'm going to do, I'm going to select the domain. I'm going to free the bake. That is going to cause everything we baked to be deleted. I'm going to select my flow object. I'm going to go back to frame, this frame where we set the value for density and fuel. Let's increase this fuel value to something like four, four, why not? Preside to add new key frame value. Let's go here where we have a next frame for the viewport. No, not here, little bit back. Okay, here, let's increase this value to four as well. Press AD to add a new keyframe, open the domain, reset your domain. Make sure to always reset your domain before baking. And now let's press Baikal, and once again, let's wait for this to finish baking. And also, if you're wondering why we need it to enable is resumable Well, to show you that, I will need to pause my bake. To pause my bake, I will need to press escape. Simply press escape to pause the baking. Now that we pause the baking, we have two buttons. We have free and resume. Resume will cause the baking to continue as if it was never stopped and free is going to basically erase all your progress you made up until this point and you will need to start from the scratch. You'll basically need to bake your entire simulation from the scratch. However, if we haven't enabled this resumable option, then we would have only this free button. We wouldn't be able to continue. The baking, we would have to free and then bake everything from the scratch. However, guys, I strongly advise you to avoid pausing your baking as much as possible. Why? Because when you pause the baking and then continue what can happen is your simulation can be a little buggy and glitchy. However, if you don't pause the baking, if you simply let it play from start to finish without pausing, then you will not have those issues. So I would strongly advise you to avoid pausing the bake as much as possible and only to do it when it is absolutely necessary. So I'm going to free the bake. Now I'm going to reset my simulation. Press bake, and let's wait for this simulation to once again finish baking. And I think this is going to be the last bake we are going to make. All right. My viewpod has finished rendering. Then I'd say that this looks very, very, very good. There is only one thing I would like to change, but only one. I think that this fire appears a tiny bit too quickly. It needs to grow a tiny bit slower. So I'm just going to once again, delete my bake free, my bake, sorry. And now, this is what I'm going to do. Let's look for a frame where this appears. It's this frame. Press these two dots to delete these keyframes. Let's go to this frame here. Okay. Now press this to 4.5 and press these two dots, and I believe this is going to be good enough. Let's reset this scale. Let's reset this simulation, and let's bake it one last time. I'm actually so confident that this is going to work that I'm not even going to bother to make the fifth viewport render. So yeah, let's just wait for this to finish baking. The latest fire has just finished baking, and I know I said I'm not going to render the viewport, but I changed my mind. Okay, looks like this looks really, really good. We are finally getting a really nice dancing fireball. So yeah, there is only one thing left to do now, and that is to give this fireball a texture. We are going to do that in the next lesson. And for now, if you manage to get this far, I want you to tap yourself on the back a little because congratulations, guys, you just passed the most difficult part of making fire simulation. Texturing in comparison to this is a piece of cake. So see you guys in the next lesson where we are going to discuss how to give your fire a decent texture. 4. Texturing and compositing: Welcome back. In the previous lesson, we finished making this fire simulation, and we made a really good one. However, there is still one thing this fire simulation is missing, and that one thing is texture. We still need to give this fire simulation a very decent texture. So how are we going to do that? Well, first, what we need to do. We need to switch our render engine to cycles, switch these to cycles, and simply prepare everything as if you were preparing for the final render. Now I'm not going to talk too much about how to set up your render, since that is a topic that deserves its own class, but I can make that class in the future. Okay. After you have finished setting up your render settings, go to shading like this, select your domain. And here we have our fire texture. Let's allow this to load. We already have a pretty good. We already have a decent texture for our smoke. However, we only have our smoke. Where is our fire? Well, to make our fire appear, we need to use this black body intensity. If we increase this from a value of zero to a value of 0.5, you can see that our fire has came back. If we set this to the value of one, you can see that our fire is now even brighter. However, you can set these to values higher than one. You can set this to a value of 25 or to a value of 50 you can basically go as far as high as you want with this black body intensity and higher you set this value, the brighter your fire is going to be. Now, this is a tiny bit too bright for my taste, so I'm just going to set this to 25. Okay, this fire already looks pretty decent, but there is actually so much more we can do to improve this texture even more. To improve this texture, we need to add volume info. Simply add that node and then take this flame and plug it into the black body intensity. All right. Now, our fire is a bit too dark now. So to fix that, let's add a mat node, switch this node from add to multiply and place this node between volume info and principal volume. All right, our fire is still a tiny bit too dark, but by changing the value on the multiply node, we can control how bright this fire is going to be. Let's switch this to a value of 25. And this is giving us a very decent value for our fire. And now, just to demonstrate, this is how our fire looks with volume and with multiply and this is how it looks without those values. And as you can see, with volume info, this fire looks a lot more detailed. However, there are still a few things we can use to make this fire look even better. Let's put some distance between these two nodes, and next, we need to add a color ramp. Okay. Now plug color ramp between these two nodes. And now by changing the values on the color ramp, we are changing the set of fire in this simulation. First, let's switch this from linear to constant, and now look carefully, select your light value, and by changing its position, you can basically control how much fire you are going to get in your simulation. If we set this to a position of 0.75, we have a little value. If we set this to the value of 0.5. Now as you can see, we are getting more fire if we set this to a value of 0.25, now, as you can see, we have a lot more fire. So simply play with this position until you get the amount of fire that you like. Now, I think this is a tiny bit too much fire, so I'm going to switch this to 0.35. Okay, I believe this is going to give us a very decent result. And now, guys, at this point, what we can also do to get a better fire, let's actually move to get a close up of the fire. Now, at this point, what you can do is you can also press this plus button to add a new black color, make sure this new color is black. Let's actually zoom out a tiny bit, just so this view port can render faster. Now, if we play with this value of this new black color we made, we are going to get a different result. If we move this black color to the position of 0.5, if you look carefully, you will notice that we are getting a new shading effect for our fire. If we move this fire, if we move this black color, a bit closer to the left to the bit like 0.4. Okay, you can see that our fire now has a lot more controlled brightness than it did before. And if you move it all the way to the right, you can see that our fire now has a lot stronger brightness than it did before. So simply, move this black color around until you get the contrast of brightness on the fire that you like. All right, I believe that the value of 0.4 is going to give me a very decent result for my fire, but there is something I would like you to know at this point. Don't blindly copy everything I'm going to do. Simply play with these values around a bit, play with these colors, and see what works best for you. For example, if I switch this from constant to B spline, the colors are now looking a lot different. Now, what has exactly happened? When this color ramp was set to constant, the contrast between bright and dark areas of our fire was very, very sharp. But now that we switch this type to be splint, what is happening is the dark and light values are blending into one another. As a result, we are getting this fire that is looking very different now, since we change this to be splint, we will need to once again put a different values of fire on this color ramp. So simply play with these values. And, as you can see, by rearranging the way these colors are set up and by changing this type, you can see that we are also getting a different look for our fire. So the point I'm trying to make, don't blindly copy all I'm going to do simply play with color ramp and play with multiply. Try getting different values for these two nodes, and that way you are going to learn something new, you are going to learn new tricks that are going to help you to make a lot better fire. The fastest way to learn fire simulation is by playing with it and experimenting. So experiment with different combination of colors here and with different values of multiply, and you are going to get something that looks really, really beautiful. Okay. Now that we set this B spline, I think that this fire looks a lot better when this color ramp is set to B spline. But there is still one more thing we can do to make this fire look better. Move this color ramp up a bit and pull these three nodes to this side. Duplicate this multiple node and place it here. Now, what you need to do add a new color ramp plug this density into the color ramp and plug this color into the value of this multiply node. Now, once again, switch this from linear to constant. And now cause black and white color to switch places, put white on the left side and put black on the right side. Okay, now by changing the position of this black color, what you can control is how strong is this brightness of the fire going to be. If we give this black color, the value of 0.25, you can see that now our fire is a little less bright, but it also has this interesting contrast of colors. And what you can also do is you can switch this also to be spline. And you can also you can also play with the position of this white color in order to get a good contrast of color for your fire. Okay. So yeah, this is how I usually set up my fire. But like I said, don't blindly copy. All I'm doing in this tutorial, play with different values on color ramp, play with different positions, and you are going to learn new tricks that are going to help you to make a beautiful fire. And one more thing you can use to improve this fire. Let's add a new Mt node. And place it here between volume info and color ramp. Make sure that this math node is set to add basically, basically, by changing the value of this new node, you are controlling how strong is going to be the effect of this second color ramp. If we switch set this to a value of zero, you can see we have a lot brighter fire if we set this to negative 0.5 you can see that our fire also became a lot more bright. Let's set this to negative one. Okay, I'd say that this value looks really, really good and is helping us make a really good looking fire. Okay, with this, we have pretty much finished making this fire simulation. We nicely set it up and we gave it a decent texture. However, there is still one more thing that you can use to make this look better. Now, I'm not going to talk about compositing much because compositing is a topic that deserves its own class. However, in this lesson, I'm going to just briefly show you how you can use compositing to make this fire look a lot lot better. So let's go back to layout. And now, in order for this trick with compositor to look to work, we need to add a camera, simply add camera into your inning blender and position it somewhere where you can nicely see your entire fire. Now, open the world properties, and let's open this render viewport. Now, our fire would, I believe, look best if we had a black background. However, if we switch the color of the world to pure black, you can see that we have a problem. As you can see, this black background looks really, really good. However, as long as this background is black, we are not getting any light from the world. The only light we have in this scene is light from the fire. Now, because of that, we can see the fire, but we can't see the smoke. And on the contrast, if we switch this background color to white, you can see that now we have the opposite problem. Now we can clearly see both the fire and the smoke. But this white background is very ugly. So how can we both see our smoke and have a nice black background? Well, we are going to do that with the compositor. First, open this world color and simply pick a value that you think is going to give you the best possible result. I believe this is going to give me act very decent properties for the fire. Next, what we need to do, go to the compositor, make sure you have use node enabled, and after that, go back to layout. Render image and simply wait for your image to finish rendering. All right. My image has just finished rendering. But, guys, I made one mistake. There is one step I forgot to do. Basically, before you render your image, go to the render properties, scroll down under the film, open the film properties, and make sure to enable transparent. What transparent? Let's open this. What transparent is going to do is pretty much it's going to make your background is invisible. It is going to cut it out of your final render. So now that you enable transparent, open render and simply select render image, All right, my new viewport has just finished rendering, and now we have this background nicely cut out. Now, what you need to do, go to the compositor, and now you can see we have our fire in the background. If you want to shrink this image, press. That is going to cause it to shrink. And if you want to cause it to grow, press this old V, and that is going to cause this image to increase. Now, we need to bring back our background, but we need to cause it to be black. So for that, simply type Alpha over, plug it here. Make sure that your render view render layer is plugged into the second image. Switch this image to pure black, and now plug this Sulfa into the factor. Okay, now, as you can see, now we have this very beautiful and very decent fire and smoke with black background. And also, if you want the effect of the compositor to be visible in your viewport, you can press this con here. If you select this sable, then the effect of the compositor will be invisible. If you select the camera, the effect of compositor will be visible, but only while you are looking at your scene through the camera. And if you select always, the effect of the compositor is always going to be visible regardless of whether or not you are looking at your scene through your camera. Okay, with this, pretty much, you conquered the fire simulation. 5. Effector: One last thing you should know about fire simulation. I made this very quick and very simple fire simulation to show you what I'm going to talk about. And to make this work, I needed to cause fire to quickly burst up. To cause that behavior under the flow of object, I gave this initial velocity Z value 100 and that is going to cause the fire to quickly burst upwards. Okay. Now, why did I make this scene? What is it that I would still like to show you? Well, let's actually add a simple cube, move it up here. And let's make it wider, a tiny bit. Now let's press Control A, and let's reset it scale. Now, let's let this animation play or even better. Let's give this animation really low resolution. Let's set this to all. And now let's just wait for this to quickly bake. And let's see what is going to happen. All right. Now that this animation has finished baking, let's see what is going to happen. Now, as you can see, this simulation has one problem. The second this fire touches this cube. This fire doesn't actually interact with it. The second, this fire touches this cube, it just passes through it like it's not even there at all, but this is not good. A real fire interacts with objects that are around it. So how can you cause your fire to interact with this cube and with the other objects? One word effector. If you select this cube and go under the physics, simply enable fluid, switch this type to the effector. Now, let's actually rebake this simulation from the scratch and let's actually make it shorter. Let's make it last 125 frames. Because demonstration this demonstration doesn't require this animation to be that long. Press Ball, and let's wait for this to finish baking. Okay, this simulation has just finished baking. Let's see what is going to happen now. Okay. Now, as you can see, now that we set this cube up as the effector, now once this smoke touches it, it is no longer passing through it. Now it is actually interacting with this cube. So yeah, anytime you want to add an object that needs to interact with fire and smoke, make sure to set that object up as the effector, and that object is nicely going to interact with your fire and smoke. However, a factor also has a few settings that we need to talk about. The first setting we need to talk about is this surface thickness. By default, this is set to zero, and what surface thickness controls is how close to your flow object smoke needs to get in order to interact with it. Now for demonstration, let's set this surface thickness to the value of two. And now let's free the bake, reset this simulation. Now let's leave this to bake and let's see what is going to happen. Simulation just finished baking, and let's see what is happening now. Okay. As you can see, our smoke is now behaving differently. Before, when this surface thickness was set to zero, this smoke was interacting with this cube only once it touches it. But now when we increase this surface thickness, now this smoke is interacting with this cube even before it touches it. So this is basically what surface thickness setting controls. These settings controls how close to your how close to your object smoke needs to get in order to interact with it. If we set this value to zero, smoke is not going to interact with your object until your smoke touches it. And if we set this value to two, smoke is going to interact with this object even before it touches it. But there is still one more thing we need to talk about. And for this, let's delete this cube. Now, free this bake. Make sure to reset your simulation. Now simply add a plane, move it up, scale it, press Controller to reset the scale, fluid, and set this type as the effector. Now, let's let this animation bake. Let's let this animation to bake, and let's see what is going to happen. Simulation finished baking and I let this plane. Now, as you can see, this smoke and fire are still passing through this plane, even though this plane is clearly set up as the effector. Now, why is this happening? Well, effector was always struggling a bit when was assigned to the plane. This plane is a surface that is infinitely thin, and that is causing some trouble when calculating how should this smoke interact with it. However, what fixing this problem is very simple. Simply enable this setting here. And now let's free this simulation, reset it, rebake it, and let's see how this smoke is going to behave once this finishes baking. All right, Bake was finished. And now, as you can see, now this fire and smoke are nicely interacting with this plane. So yeah, always just make sure that you enable this Esplaner. If your object for a factor is plane, this is just going to help you to get a little better result. Or you can also simply increase surface thickness to one. That is also going to give you similar result as the Is planar setting. Now there is also one more thing we need to discuss, and that is these subframes. Now, if you were paying attention, you know that this flow object have subframes and what flow objects do is they calculate, how should this fire behave between frames? And now, these subframe settings is giving you also a similar result on the effector. What subframe settings are going to do? Is there going to calculate? How should your smoke behave between frames while it is interacting with the effector object? The higher you set this value, the smoother this setting is going to get. Just like with the flow object, I highly recommend you to not set your subframes for the effect or too high, to not add too much pressure on your flow object. And with this, we covered everything we need to discuss about fire simulation. 6. Outro: Congratulations, guys. You made it to the end of the class. I encourage you to show others your beautiful work in the class projects below, and I hope that you will put this new knowledge to good use. Thank you for the attention. And if you have any questions, feel free to ask. See you in the next class. See.