Mesh in Metal IOS

Question

I am new to MTKMesh/MDLMesh any online resource material to create a Creating a Custom Mesh in 2D. I have the Vertex data.

init(vertexBuffer: MDLMeshBuffer, vertexCount: Int,  descriptor: MDLVertexDescriptor, submeshes: [MDLSubmesh])

I hope to use this function. Any suggestion to create MDLMeshBuffer,MDLVertexDescriptor, Submeshes

Answer 1

Suppose you have a Vertex struct with a single float2 member representing position. You might start with an array of such vertices ([Vertex]) and an array of 16-bit unsigned integer indices ([UInt16]).

Then you might do something like this:

let device = MTLCreateSystemDefaultDevice()!
let allocator = MTKMeshBufferAllocator(device: device)

let vertexBuffer = allocator.newBuffer(MemoryLayout<Vertex>.stride * vertices.count, type: .vertex)
let vertexMap = vertexBuffer.map()
vertexMap.bytes.assumingMemoryBound(to: Vertex.self).assign(from: vertices, count: vertices.count)

let indexBuffer = allocator.newBuffer(MemoryLayout<UInt16>.stride * indices.count, type: .index)
let indexMap = indexBuffer.map()
indexMap.bytes.assumingMemoryBound(to: UInt16.self).assign(from: indices, count: indices.count)

let submesh = MDLSubmesh(indexBuffer: indexBuffer,
                         indexCount: indices.count,
                         indexType: .uInt16,
                         geometryType: .triangles,
                         material: nil)

let vertexDescriptor = MDLVertexDescriptor()
vertexDescriptor.attributes[0] = MDLVertexAttribute(name: MDLVertexAttributePosition,
                                                    format: .float2,
                                                    offset: 0,
                                                    bufferIndex: 0)
let mdlMesh = MDLMesh(vertexBuffer: vertexBuffer,
                      vertexCount: vertices.count,
                      descriptor: vertexDescriptor, 
                      submeshes: [submesh])

let mesh = try? MTKMesh(mesh: mdlMesh, device: device)

If your vertex type is more complex, you'd adjust the vertex descriptor accordingly.