The Particle Sampler Info node is a particle utility that lets you:
- Use particle object attributes (including ramps and particle expressions) to drive particle shader attributes on a per-particle basis.
- Use rgbPP and opacityPP attributes in software rendering. Previously, you could use these attributes only in hardware rendering.
- Have more control over texture placement nodes for particles, including the use of per-particle attributes for texture coordinates.
The Particle Sampler Info node provides all the functionality of the particle color mapper, transparency mapper, incandescence mapper, and age mapper. See Particle Sampler Info node attributes and Create a Particle Sampler Info node.
Using the Particle Sampler Info node
The Particle Sampler Info node provides particle shape attributes to either a particle shader, texture, or texture placement node for use in software rendering.
When you use a Particle Sampler Info node, you connect one or more of its outputs to attributes of a particle shader or texture placement node. This tells the shader to get the per-particle information from the Particle Sampler Info node. It also tells the Particle Sampler Info node which attributes to get from the particle shape.
Types of outputs
The Particle Sampler Info node has the following types of outputs:
- A uv coordinate output designed to drive the uv coordinate input for texture placement nodes. This is somewhat like the output from the old particle utilities, but more powerful. See Set Particle Sampler Info node attributes and Create a Particle Sampler Info node.
- Outputs that correspond to predefined attributes of the particle shape, such as Rgb PP. These are used to drive attributes of shaders or textures on a per-particle basis.
- Ten predefined outputs for user-defined attributes that you can add to the particle shape. Five are scalar attributes and five are vector. See Add user-defined attributes.
- Two outputs, birthPosition and worldBirthPosition, that correspond to two optional attributes (with the same name), which you can add to your particles. Note:
You still have to add attributes to the particle shape, where applicable. The Particle Sampler Info node just gets attribute values, if they are present. For example, making a connection from the Particle Sampler Info node parentU to the shader tells the sampler info node to get parentU if it’s there, and use it in the shading. You still have to add parentU to the particle shape.
The Particle Sampler Info node has no association with any particular camera, unlike the samplerInfo node. The two nodes are similar in that both provide data to shaders to use in shading samples. They are different in that much of the data the samplerInfo node provides is camera-dependent.
Strategies for using the Particle Sampler Info node
There are two basic strategies for using the Particle Sampler Info node to control your particles:
- The first strategy uses the Particle Sampler Info node to drive a texture placement node. The setup is:
The advantage of this strategy is two-fold: you can use any type of texture, and you can use the controls on the texture placement node.
- The second strategy uses the Particle Sampler Info node to feed per-particle attributes, such as rgbPP, directly to the shading or texture node. The setup is:
The main advantage of this strategy is that it lets you control the per-particle attribute using expressions, ramps, or the Component Editor and see the result in the shading or texture node.
Use user-defined attributes
In addition to its many outputs for predefined attributes of the particle shape (such as position, radiusPP, and so on), the Particle Sampler Info node includes ten predefined outputs for user-defined attributes, which you can add to the particle shape.
Five of these are scalar and five are type; they are called userScalar1PP, userVector1PP, and so on.
If you connect one of these to a shading attribute, the Particle Sampler Info node looks for an attribute of the identical name on the particle shape, and fetches those values. For example, if you connect userScalar1PP to shader noise, then the Particle Sampler Info node looks for a userScalar1PP attribute on the particle shape.