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An unlit surface shader, constructed from emission and transmission values. It represents a surface that can emit and transmit light, but does not receive illumination from light sources or other surfaces.
Karma can render unlit surfaces so they don’t emit any light into the scene. Use a Render Geometry Settings node, to set Light Source Diffuse Scale and Light Source Specular Scale to 0.
This shader is useful for glowing/emissive particles.
Create emissive particles
You can use this shader to emit light from particles, e.g. from a POP Network OBJ.
On the stage level, press ⇥ Tab to open the Tab menu. From there, create SOP Create LOP.
Click the node’s name and rename it to
Double-click the node to dive into it.
Inside the SOP Create LOP, add a particle source object. This can be any geometry, e.g. a Sphere SOP.
Add a downstream POP Network and connect its first input with the output of the sphere.
popnetto dive into it.
Inside the POP Network you can see a complete and fully working network. When you go to the Playbar and click to start the simulation, you will see that new particles are added, but they remain static. You need a force to move the particles.
Press ⇥ Tab again, and add a POP Force DOP.
Place the node between
wire_pops_into_hereto connect the force.
On the Noise tab, set Amplitude to
On the Birth tab, change Const. Birth Rate to
200to decrease the number of particles.
Return to the stage level.
The material lets you define emission strength and color.
Add a Material Library LOP and connect its input with the output of the
particlesSOP Create LOP.
Double-click the new node to dive into it. There, lay down an USD MaterialX Builder VOP. This node is basically a modified Sub Network VOP.
Dive into the
mtlxmaterialnode, create the MtlX Surface Unlit VOP node and connect its output with the input of
Increase Emission to make the lights brighter, while Emission Color tints the particles.
Return to the stage level.
Assign the material
You must assign the material to the particles through paths to see the lights.
Add an Assign Material LOP and connect its input with the output of
For Primitives, enter
/particles. This is the path to the SOP Create LOP.
For Material Path, enter
/materials/mtlxmaterial. This path points to the
mtlxmaterialsubnet inside the library.
You can see a graphic representation of the network’s hierarchy in the Scene Graph Tree pane. You can also drag elements from the Scene Graph Tree to the parameters of the Assign Material LOP.
Surface emission amount. Multiplier of the Emission Color.
Color emitted by the surface.
Surface transmission amount. Multiplier of the Emission Color.
Color transmitted through the surface.
Surface presence, useful for cutting out shapes with images or other signals.