Fire Tutorial. By: Shane Trautsch Crestwood High School

Transcription

1 Fire Tutorial By: Shane Trautsch Crestwood High School Blender 2.68 In this tutorial you will learn How to use the smoke simulator How to create fire Use Materials and textures Bake and render animations Optional Using keyframes and textures This tutorial is meant to introduce you to the smoke and fire simulator. It is not made to fit every fire simulation. Simulations takes patience, practice, and a very good computer. Use the fire on this first page as a reference. Pay close attention to the colors, you will need them for later. Good Luck!

2 First open up a new blender file and select the cube using the RMB or B. Scale up the cube(s) like so This cube is going to be the domain for our simulation. The Domain is basically the area that the simulation occurs in. NOTE A smaller domain will result in a shorter render times. Make sure you keep your domain as small as possible! Go to the Properties bar and click on the tab to the far left, the physics tab. This tab holds all of the different physics system blender uses. For now, click on smoke button.

3 Check the box marked smoke adaptive domain, and the box marked dissolve. Also change the vorticity to 3 Why should you do this? The adaptive smoke domain will make blender put the smallest possible domain around the smoke which cuts down on render time. The dissolve boxes will make the smoke dissipate instead of remaining until it exits the domain (if it is not checked there seems to be too much smoke and it doesn t look very realistic). NOTE: If your computer is slow you might want to turn down the divisions while working on the blend before the final render. This will make the flame look worse, but it will speed up the processing time. The vorticity will affect the turbulence the smoke has, I've found a value of 3 to be better for fire scenes. Next, we are going to add a plane in that will emit the smoke and fire. Press Shift C to center your cursor and then press the shift A, and go to mesh plane. Once again(under the properties tab) go to the physics tab (Far right) and click on smoke. Select Flow, this will make the plane an emitter. Now change the smoke settings to fire & smoke. Doing so will add flames to the smoke.

4 Now go ahead and press Alt A and you should see fire! Congratulations! Step one is complete! STOP Save point make sure to save your project frequently, blender is prone to crashing when working CPU intensive projects like fire simulations. Step 2 Materials and textures Part 1 Materials Now that you have saved go ahead and render your picture (on windows F12) Did you get a cube? What happened to all your work?

5 Press esc to go back to normal view Don t Panic! What happened is the cube still has density, meaning you can see it. Your fire, while it looks good within blender, has no texture or material yet. Which means it's not ready to be animated. In order to fix this we need to change the way blender sees the cube. Go ahead and select the cube using RMB or B. Add a material using the Properties tab. Now change the material type from Surface to Volume You can change the Density to 0, the Density scale to 5, the Emission color to black, and the Scattering amount to 3 or 4. Also Check External Shadows.

6 Reasoning The density is changed to 0 because it allows you to see through the cube. The density scale effects how dense the smoke is. Generally 1 is too low, a value of 4 or 5 works best. Scattering affects how light gets hit by the smoke, it allows you to see the smoke. Lastly, the emission setting affects how much like the smoke casts out, it can be a good idea to turn this up when rendering fire, but it can take tinkering. I will set the emission color to black and leave an emission value of 0. External shadows will allow shadows to move through the cube, if you have more objects in the scene this will make it look more realistic. Part 2 Textures Now we need to texture the smoke and fire, this is going to make it visible. Go to the Properties tab and click on the texture tab (one left of the materials tab) If there is a texture set up click the X and delete it. Notice how near the top of the texture it says Cube Material This is what you're applying this texture too, which is a good thing to take notice of. Add a new texture. Select Voxel data. The word voxel comes from pixel and volume (ex. Minecraft is voxel based). You can name this texture smoke. Change the domain object to be your cube and the influence to include only density. The influence is going to apply a smoke texture to the voxels based on their density. This will make the smoke look more realistic.

7 Render and it should look something like this. It doesn't look the best, but we are getting somewhere now! Note: If your picture shows just a cube. Make sure the animation is playing when you are running the smoke simulator without rendering.

8 To add the flames, we must add another texture Select voxel data and select the domain object as your cube Change the source from Smoke to Flame this will change the what the texture is applied too. For influence select Emission with a value of 5 and check Emission color.

9 Heres the tricky part, under the color tab click ramp, make a color scheme like the one below. This is going to color the smoke. NOTE It helps to turn the alphas of the color points to 1. (By clicking on the solid color bar you can change the color of the line you have selected) Make sure to play with this as it paints the smoke so to say. This part is very challenging to get right because it is a strong influence on the flames. Notice that the right hand side affects the center of the flame, which is hotter, and the left side effects the edges of the fire Now you can go ahead and render (F12). You've created fire! Good job! Now lets make it look good!

10 Part 2.5 Optionals This part of the tutorial is all about making the fire more realistic. If you have noticed, right now the fire stays in the same area the entire time. We are going to use a texture to change this. First press A to deselect all objects and add in a new texture. Click the color ramp and bring the two color points closer together to give the texture more contrast. Don t forget to name the texture something you wont forget. Now select the plane using RMB or B and go to this physics panel. Now you want to use advanced smoke options and add a texture, make it the one you just created. This is going to set the smoke to animate on the black parts of your plane(the part with volume). If we want it to move we have to make the texture change. Use the offset value this is going to change how the texture is set on the plane. Use the timeline to do this. The timeline shows what is happening each frame of an animation. (30 frames = 1 second of animation). Enter a value of 3 for the offset, hold your cursor over it and press I. What you have done sets the offset value to be 3 at that particular frame. By setting values like this(blender adds in the frames in between) it makes the fire appear to move around the smoke. Note Try changing the type of texture and see what different effects you get. Try to add in about 4 5 keyframes. Play with it, see what looks the best to you!

11 . Note Turning the world color black, while optional, really makes the fire pop Great job! Now we are moving on too Part 3 Baking and rendering Before we begin this I'm going to make a list of some common variables to change in order to make your fire look better. Domain Physics panel These three setting strongly affect your final renders. Divisions A higher setting of this will divide the smoke into more particles, making it smoother. A high quality render would be a value of 80 Found in Smoke domain object s(cube) Physics tab Smoke High Resolution This applies a multiplier on the divisions, making the smoke look a lot better. I strongly recommend checking this before doing a final render. Found in Smoke domain object s(cube) Physics tab Domain materials settings gradient step size If you notice your fire looking very grainy, this will fix it. Under the integration heading(under materials) a low step size will get rid of the grains. For final renders I normally use a value of.02. Found in Smoke domain object s(cube) Material tab.

12 Before you can render your final animation it must be baked. Make sure you have saved your file, and go to your smoke domain object s physics. Under the Smoke Cache drop down menu there should be an button called bake. This is going to do all the calculations for where the fire will move, within a certain number of frames. When it is processing this your cursor should turn into a black square and a number will pop up. The number is the percent completed. Note You have to save your project before using the smoke cache Almost done! All thats left is to render your animation. Position the camera where you would like. Then go ahead and click render animation. Congradulations! You have made fire! I hope you learned a lot from this tutorial. Like said before, this tutorial is just the beginning. Be creative! Anything is possible with blender! Note: You may want to compile your animation in Movie Maker or a similar program

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