My code is based off: https://medium.com/@warrenm/thirty-days-of-metal-day-12-mdlmesh-and-mtkmesh-1a9f57400e2d Running https://github.com/metal-by-example/thirty-days-of-metal/tree/master/12/MetalMTKMesh shows the error.

This is what they look like in 3D

I think I found the problem. This works except on 12.6.4 let mdlVertexDescriptor = MDLVertexDescriptor() mdlVertexDescriptor.vertexAttributes[0].name = MDLVertexAttributePosition mdlVertexDescriptor.vertexAttributes[0].format = .float3 mdlVertexDescriptor.vertexAttributes[0].offset = 0 mdlVertexDescriptor.vertexAttributes[0].bufferIndex = 0 mdlVertexDescriptor.vertexAttributes[1].name = MDLVertexAttributeNormal mdlVertexDescriptor.vertexAttributes[1].format = .float3 mdlVertexDescriptor.vertexAttributes[1].offset = 12 mdlVertexDescriptor.vertexAttributes[1].bufferIndex = 0 mdlVertexDescriptor.bufferLayouts[0].stride = 24 vertexDescriptor = MTKMetalVertexDescriptorFromModelIO(mdlVertexDescriptor)! This works everywhere let mdlVertexDescriptor = MDLVertexDescriptor() mdlVertexDescriptor.vertexAttributes[0].name = MDLVertexAttributePosition mdlVertexDescriptor.vertexAttributes[0].format = .float3 mdlVertexDescriptor.vertexAttributes[0].offset = 0 mdlVertexDescriptor.vertexAttributes[0].bufferIndex = 0 mdlVertexDescriptor.vertexAttributes[1].name = MDLVertexAttributeNormal mdlVertexDescriptor.vertexAttributes[1].format = .float3 mdlVertexDescriptor.vertexAttributes[1].offset = 16 mdlVertexDescriptor.vertexAttributes[1].bufferIndex = 0 mdlVertexDescriptor.bufferLayouts[0].stride = 32 vertexDescriptor = MTKMetalVertexDescriptorFromModelIO(mdlVertexDescriptor)! Seems related to: https://forums.kodeco.com/t/chapter-5-starter-project-stride-number-when-setting-normals/60781/8

Appears to be fixed in 12.6.8

Both issues still present in Sonoma 14.5 using Xcode 15.4

Both issues still present in Sonoma 14.6

No joy with Sonoma 14.7. Sigh.