vorg
commented
4 years ago After looking at that SceneKit shader modifiers our api could look e.g. like this:
material.shaderModifiers = {
// model space, before skinning, world transform and projection
geometry: `
uniform float uDisplaceAmplitude;
vertexData.position += vertexData.normal * uDisplaceAmplitude;
`,
// after reading all uniforms and texture values
// before lighting, values in view space
surface: `
vec3 textureTriplanar(vec3 worldPos, vec3 normal) {
...
}
surfaceData.baseColor = textureTriplanar(worldPos, worldNormal);
`
// after lighting (but before or after exposure and tonemapping?)
fragment: `
outputData.color.rgb = vec3(1.0) - outputData.color.rgb;
// but also
outputData.color.rgb = surfaceData.normal * 0.5 + 0.5;
`
}Notes
- geometry is run in vertex shader, surface and fragment in fragment shader
- surface stage assumes value in view space but we already compute values in world space e.g. for envmaps, those could be available too
- SceneKit includes another
lightingstage that can execute in vertex or fragment shader - SceneKit allows modification of texture coordinates, which means colors from textures are read after this stage
- fragment state in SceneKit is the final pixel color
Open questions: How do you do you define uniforms?
- we could detect and extract uniforms and functions as assumed in above example
- we split modifier into declaration and code parts
material.shaderModifiers = {
// model space, before skinning, world transform and projection
geometry: {
defs `uniform float uDisplaceAmplitude;`,
code: `vertexData.position += vertexData.normal * uDisplaceAmplitude;`
}
`,
simonharrisco
dmnsgn
pailhead
Currently we can set
material.vertandmaterial.fragbut that breaks as we also include them in the depth prepass shadersvert: material.vert || DEPTH_PASS_VERT. The correct (needs testing) way is to define all 3 shaders and use preprocessor to support all 3 casesThat's painful.
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