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Making Fire with ICE, Part II: Rendering the Flames

If you went through the basic example of creating a fire in Making Fire with ICE: A Particle Walkthrough, you can add shaders to it to render it.

There are several standard particle shaders and shader compounds that you can use to start. Once you start to understand the effects of the shaders, you can add more shaders and tweak the parameter values to get just the right look as you like it. The following example is just a simple render tree to get you started.

If you’re using the fire scene you created in the first part of the example, you need to first make a few changes to the particles:

1. Select the point cloud, open the ICE tree, and then open the Emit from Surface compound’s property editor and make these changes:

- Change the Size of the particles to something quite large like a value of 2. This is because you’re going to render the particles as a volume into whose density you’re going to “cut” and shape.

- Make sure the Shape is something volumetric and slightly elongated, like a cone or Capsule.

Now you’re ready to apply the shaders:

2. With the point cloud still selected, open a render tree (press 7).

3. By default, you’ll see a Phong shader attached to the point cloud’s Material node.

You’re going to render the particle’s volume, not the surface, so for that you need a Volume shader. In this case, you’re going to use the Particle Renderer shader compound, which contains several shaders that help you achieve the volumic look (see ICE Particle Shader Compounds).

4. From the preset manager on the left of the render tree, select the Particle group and drag the Particle Renderer shader compound into the render tree workspace.

5. Plug its output into the Volume port of the Material node.

You can also delete the default Phong shader, or at least disconnect its outputs that are plugged into the Material node.

6. Now make the following connections so that you end up with a render tree that looks like this:

- From the Particle group in the preset manager, drag in the Particle Gradient Fcurve compound and plug it into the Global/Gradient Density port of the Particle Renderer compound. This contains a curve that allows you to shape the volume density.

- From the Particle group, drag in the Particle Gradient shader and plug it into the Global/Gradient Color port of the Particle Renderer compound. This contains a color gradient that lets you color the flame. See Particle Gradient Shader for information on this shader.

- From the Texture group, drag in the Fractal Scalar shader and plug it into the Density Shape port of the Particle Renderer compound. This shader lets you create fractal noise on the flame’s shape so that it’s more random looking. See Fractal and Cell Scalar Shaders for information on this shader.

For the sake of learning, you just went through the process of hooking up shaders from scratch. For the sake of speed, however, you can choose Get > Material > ICE Particle Volume from the Render toolbar to do most of this work for you. This command applies the Particle Renderer shader compound to the Volume port on the point cloud’s Material node. As well, it plugs the Particle Shaper shader compound into the Shape Density port on the Particle Renderer shader compound.

Once you’ve got the shaders hooked up together, it’s time to set up some basic parameters. Change only the parameters described here for now and leave all other settings in the default values.

Later on, you can go back and tweak these parameters and others with the render region drawn over the flame. The settings described here are just to get you started ...

For more information on any of these parameters, click the ? icon in each of the shader’s property editor to open the online help for that shader.

7. Set these parameters in these shader property editors:

Particle Renderer shader compound:

Particle Gradient shader:

On the Gradient Position tab, set these parameter values:

On the RBGA Gradient tab, make the color gradient look something like this:

Fractal Scalar shader:

Particle Gradient Fcurve shader compound:

Make the curve look something like this:

8. Continue tweaking the shader parameters to get the results that you want. This is just the beginning!

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