Examples: Added webgl2_volume_instancing example. #19992
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mrdoob
commented
Aug 2, 2020
mrdoob
commented
| void main() { | ||
| vec4 worldPosition = modelViewMatrix * instanceMatrix * vec4( position, 1.0 ); | ||
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| vOrigin = vec3( inverse( instanceMatrix * modelMatrix ) * vec4( cameraPos, 1.0 ) ).xyz; |
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I'm not sure what you are computing here. Inverting a matrix may be avoidable.
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Not, sure... I don't have a 100% understanding of the code yet. It was done by @spite.
The technique es pretty much the same as in this article:
https://medium.com/@babylonjs/path-tracing-with-babylonjs-part-1-solids-e48be7c2ba9c
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vOrigin is the camera position in the local space of the instance, so the code looks correct.
Tricks to avoid an inverse can be found here, but they may not apply in this case. Maybe the fragment shader could be implemented in a different coordinate frame?
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We could pass the inverted camera position, but in this example we're also dealing with instanceMatrix which wouldn't work.
Changing the fragment shader is indeed an option but, it doesn't seem like that matrix inversion is the bottle neck. The bottleneck is the 3d texture size and the raymarching code.
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| for ( let i = 0; i < mesh.count; i ++ ) { | ||
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| transform.position.random().subScalar( 0.5 ).multiplyScalar( 150 ); |
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This may be a bit heavy. Consider reducing the count by a factor of 10 and scaling position by 50, instead. Looks about the same visually.
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Yes, I was trying to see how much my device was able to handle. I'll reduce it.
