Hi Caroline,
Iāve got something interesting to share:
I tried to transform a single submesh, but it was not successful. Not only the submesh that was supposed to transform transformed, all the other submeshes transformed in the same way.
I used the method you mentioned: identify the submesh that needs to be transformed by checking submesh.name
, then send the transform matrix throught setVertexBuffer
at index 21; in case it is not the submesh that needs to be transformed, send an identity matrix.
here is my code in render(commandEncoder: MTLRenderCommandEncoder, submesh: Submesh)
:
var submeshPointer = submeshesBuffer.contents().bindMemory(to: Submeshes.self, capacity: instanceCount)
for submeshTransform in submeshesTransforms {
if mtkSubmesh.name == "eyelid" {
submeshPointer.pointee.modelMatrix = submeshTransform.matrix
print("š¹ \(mtkSubmesh.name), submeshTransform: \(submeshPointer.pointee.modelMatrix)")
} else {
submeshPointer.pointee.modelMatrix = .identity()
print("š¦ \(mtkSubmesh.name), submeshTransform: \(submeshPointer.pointee.modelMatrix)")
}
submeshPointer = submeshPointer.advanced(by: 1)
}
commandEncoder.setVertexBuffer(submeshesBuffer, offset: 0, index: 21)
I printed out the submeshPointer.pointee.modelMatrix
, the results are (because there are two eyes, so I used the instances class, therefore two eyeballs/eyelids) :
eyeball, submeshTransform: simd_float4x4([
[1.0, 0.0, 0.0, 0.0],
[0.0, 1.0, 0.0, 0.0],
[0.0, 0.0, 1.0, 0.0],
[0.0, 0.0, 0.0, 1.0]])
eyeball, submeshTransform: simd_float4x4([
[1.0, 0.0, 0.0, 0.0],
[0.0, 1.0, 0.0, 0.0],
[0.0, 0.0, 1.0, 0.0],
[0.0, 0.0, 0.0, 1.0]])
eyelid, submeshTransform: simd_float4x4([
[1.0, 0.0, 0.0, 0.0],
[0.0, 1.0, 0.0, 0.0],
[0.0, 0.0, 1.0, 0.0],
[0.0, 1.0, 0.0, 1.0]])
eyelid, submeshTransform: simd_float4x4([
[1.0, 0.0, 0.0, 0.0],
[0.0, 1.0, 0.0, 0.0],
[0.0, 0.0, 1.0, 0.0],
[0.0, 1.0, 0.0, 1.0]])
You can see that the eyelidās transform matrix is different from eyeballās, as it should be, at least at this time. But after I run the app, things changed. Both eyeball and eyelid are transformed. I checked the value of vertexBuffer at index 21 in the GPU debugger and found out that they are the same value for eyeball and eyelid. Hereāre the screenshots:
vertexBuffer at index 21 for the eyeball submesh:
vertexBuffer at index 21 for the eyelid submesh:
So event if I sent different matrices for different submeshes through vertexBuffer at index 21, they still receive the same value. I donāt understand why it is like this at all.