Class ISpecularCompositeShader
class ISpecularCompositeShader : public BaseInterface
Description:
This class is only available in release 5 or later.
This class is only used to communicate some information between the MAX Standard Material and the Shaders for the MAX Standard Material. The information that the Shaders require that wasn't supplied previous is the RenderGlobalContext. This would be used by 3rd parties who want to write shaders for the MAX standard material. This is only required if the shader performs operations that are not valid for arbitrary light values. For example: Using the default values, the Physical Sun has light multiplier values that are around 60.
Several standard MAX shaders, like the Aniso and ONB shaders, composite specular highlights over the diffuse light, and the calculation looks something like:
color = diffuse * (1 - specular) + specular;
This works fine as long as specular is between 0 and 1. If specular goes above 1, you get all kinds of unusual artifacts. This calculation is done this way to prevent color clipping because of bright specular highlights. With lighting values at 60, the specular is frequently greater than 1.With an exposure control, the exposure control manages the color clipping and we can simply add the diffuse and specular components.
This interface gives the shader a chance to investigate the render parameters and decide how the lighting is to be combined.
This is usually done by using multiple inheritances and deriving the Shader Implementation from Shader and ISpecularCompositeShader.
The Shader needs to override GetInterface(Interface_ID id) and return the address of the ISpecularCompositShader interface and GetRequirements also needs to be overriden to return MTLREQ_PREPRO as one of the shader requirements.
Then the shader needs to implement ChooseSpecularMethod. The typical implementation is:
void CombineComponentsCompShader::ChooseSpecularMethod(TimeValue t, RenderGlobalContext* rgc)
{
useComposite = true;
if (rgc == NULL) {
ToneOperatorInterface* tint = static_cast<ToneOperatorInterface*>(
GetCOREInterface(TONE_OPERATOR_INTERFACE));
if (tint != NULL) {
ToneOperator* top = tint->GetToneOperator();
if (top != NULL && top->Active(t))
useComposite = false;
}
} else {
ToneOperator* top = rgc->pToneOp;
if (top != NULL && top->Active(t))
useComposite = false;
}
}
Methods:
Prototype
virtual void ChooseSpecularMethod(TimeValue t, RenderGlobalContext* rgc) = 0
Remarks:
To be implemented Material Shaders. Provides a selection mechanism for the specular methods provided by various tone operators either provided by the System or by the implementing Shader.
Parameters:
TimeValue t
Present scene time value.
RenderGlobalContext *rgc
Pointer to a RenderGlobalContext that encapsulates the shared data between a Standard Material and the implementing Shader.
Return Value:
None