[Feature] Is there anyway I can custom shader for VolumeMapper?

[zhaoangus]

Motivation

I want to mix the colors of two volumeActors that overlap each other，but I cannot find anything that works.

Detailed Description

1. I tried a blend mode which is ADDITIVE_INTENSITY_BLEND in volumeMapper, but it doesn't work.
2. I use a way to custom shader refer to PolyDataMapper，like this：

const replaceShader = (volumeMapper: vtkVolumeMapper) => {
const mapperViewProp = volumeMapper.getViewSpecificProperties()
mapperViewProp.OpenGL = {
ShaderReplacements: [],
VertexShaderCode: '',
FragmentShaderCode: '',
GeometryShaderCode: '',
}
mapperViewProp.OpenGL.ShaderReplacements.push({
shaderType: 'Fragment',
originalValue: '//VTK:CustomColorMix',
replaceFirst: true,
replacementValue: '//VTK::Color::Impl\n gl_FragColor = vec4(0.0,1.0,0.0,1.0);\n',
replaceAll: false,
})
}

But that doesn't work either.

So I wonder if there‘s a way to make it?

[finetjul]

You might want to look at this branch that has been merged into beta.