shadingEngine

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The shading engine node (also known as the shading group node) is the node that associates shaders with geometry. The shading group is a special type of object set that, in addition to containing geometry, defines a number of "shading ports" that control how the geometry in the set will be shaded. Each port is the starting point of a shading network.

The shading group has 3 shading ports:

1) surface shading port - The shader that is connected to this port will control the appearance of the "surface geometry" contained in the shading group. Maya currently has 4 surface geometry types:

- NURBS surfaces - polygonal meshes - subdivision surfaces - particle systems using the "blobby" software render mode

For each of these object types, the renderer will evaluate the "outColor" and "outTransparency" attributes of the shader attached to the surface shader port to determine the color and transparency of the objects, respectively.

2) volume shading port - The shader that is connected to this port will control the appearance of the "volume geometry" contained in the shading group. Maya currently has 3 volume geometry types:

- light fogs - environment fog - particle systems using the "cloud" or "tube" software render modes

The renderer will evaluate the "outColor" and "outTransparency" attributes of the shader attached to the volume shader port to compute the color and transparency of these volume objects.

3) displacement shading port - The shader that is connected to this port will be invoked for the purpose of displacement-mapping all of the surface geometry in the shading group. The renderer will evaluate the "displacement" attribute of the shader attached to the displacement shader port for this purpose. The surface shader port will then be used to shade the displaced geometry.

Following shading port is for mental ray for maya exclusively.

1) material shading port

2) shadow shading port

3) volume shading port

4) photon shading port

5) photon volume shading port

6) displacement shading port

7) environment shading port

8) light map shading port

9) contour shading port

It should be noted that the type of the actual shading port attributes is irrelevant, as they exist only to establish a connection between the shading group and the root node of a shading network. Connecting *any* attribute of a shader to the shading port is sufficient to establish this connection. For this reason, the port attributes are declared as type Tdata, meaning that any type of attribute can be connected to them.

objectSet

displacementShader, imageShader, surfaceShader, volumeShader

Long name (short name)	Type	Default	Flags
surfaceShader (ss)	generic typed data	NULL
The surface shader port. The node connected to this, the most commonly used port, will have its "outColor" and "outTransparency" attributes evaluated to sample the color and transparency of surface geometry in the shading group. Surface geometry types include NURBS surfaces, polygonal meshes, subdivision surfaces, and particles using the blobbly surface rendering mode.
displacementShader (ds)	generic typed data	NULL
The displacement shader port. The node that is connected to this port will have its "displacement" attribute evaluated to sample the displacement values for surface geometry in the shading group.
volumeShader (vs)	generic typed data	NULL
The volume shader port. The node that is connected to this port will have its "outColor" and "outTransparency" attributes evaluated to sample the color and transparency of volume objects in the shading group. Volume geometry types include light fogs, environment fog, and particles using the cloud or tube rendering modes.
imageShader (is)	generic typed data	NULL
Currently unused port.