Metal Compute and Tessellation

Added support for drawing and evaluation using Apple's Metal API for high performance and low-overhead GPU access.

This includes the full set of Osd interfaces needed to draw using Metal graphics rendering (including tessellation shaders) and evaluate stencils and patch tables using Metal compute processing.

Also includes an example mtlViewer that can be built to run on either macOS or iOS.

Metal Graphics Rendering with Tessellation

Metal Patch Evaluation using Compute Processing

Osd::MTLContext

• device and commandQueue member data

Osd::MTLComputeEvaluator

• Create()
• EvalStencils()
• EvalPatches()
• EvalPatchesVarying()
• EvalPatchesFaceVarying()
• Compile()
• Synchronize()

Osd::MTLStencilTable

• Create()
• GetSizesBuffer()
• GetIndicesBuffer()
• GetDuWeightsBuffer()
• GetDvWeightsBuffer()
• GetDuuWeightsBuffer()
• GetDuvWeightsBuffer()
• GetDvvWeightsBuffer()
• GetNumStencils()

Osd::MTLMeshInterface

• GetNumVertices()
• GetMaxValence()
• UpdateVertexBuffer()
• UpdateVaryingBuffer()
• Refine()
• Synchronize()
• GetPatchTable()
• GetFarPatchTable()
• BindVertexBuffer()
• BindVaryingBuffer()

Osd::MTLPatchTable

• Create()
• GetPatchArrays()
• GetPatchIndexBuffer()
• GetPatchParamBuffer()
• GetVaryingPatchArrays()
• GetVaryingPatchIndexBuffer()
• GetNumFVarChannels()
• GetFVarPatchArrays()
• GetFVarPatchIndexBuffer()
• GetFVarPatchParamBuffer()

Osd::MTLLegacyGregoryPatchTable

• UpdateVertexBuffer()
• GetVertexBuffer()
• GetVertexValenceBuffer()
• GetQuadOffsetsBuffer()

Osd::PatchShaderSource

• GetCommonShaderSource()
• GetPatchBasisShaderSource()
• GetVertexShaderSource()
• GetHullShaderSource()
• GetDomainShaderSource()

Osd::CPUMTLVertexBuffer

• Create()
• UpdateData()
• GetNumElements()
• GetNumVertices()
• BindCpuBuffer()
• BindMTLBuffer()
• BindVBO()

Improvements

• Fixed several instances of local variable shadowing that could cause build warnings
• Updated continuous-integration build scripts and added testing on macOS