Multisampling metal screen drawing

Question

How to visualize primitives in a texture without a screen, and not directly on the screen?

I have a set of triangles and the corresponding color, I just want to draw them in the same way as on the screen, but in the texture of the screen, which I can save to a file.

Can someone show me some sample code?

Answer 1

Well, I figured it out myself. This code does the job with the only exception that it draws triangles that are too large, but that’s another topic for the Vertex function.

Here is my code:

let fragmentProgram = defaultLibrary.newFunctionWithName("image_fragmentT") let vertexProgram = defaultLibrary.newFunctionWithName("image_vertexT") struct VertexT { var x, y, z, w : Float var r, g, b, a : Float } let vertexDescriptor = MTLVertexDescriptor() vertexDescriptor.attributes[0].offset = 0 vertexDescriptor.attributes[0].format = .Float4 vertexDescriptor.attributes[0].bufferIndex = 0 vertexDescriptor.attributes[1].offset = 0 vertexDescriptor.attributes[1].format = .Float4 vertexDescriptor.attributes[1].bufferIndex = 0 vertexDescriptor.layouts[0].stepFunction = .PerVertex vertexDescriptor.layouts[0].stride = sizeof(VertexT) let pipelineStateDescriptor = MTLRenderPipelineDescriptor() pipelineStateDescriptor.vertexDescriptor = vertexDescriptor pipelineStateDescriptor.vertexFunction = vertexProgram pipelineStateDescriptor.fragmentFunction = fragmentProgram pipelineStateDescriptor.colorAttachments[0].pixelFormat = .RGBA8Unorm; pipelineStateDescriptor.colorAttachments[0].blendingEnabled = true pipelineStateDescriptor.sampleCount = 4 pipelineStateDescriptor.colorAttachments[0].rgbBlendOperation = MTLBlendOperation.Add pipelineStateDescriptor.colorAttachments[0].alphaBlendOperation = MTLBlendOperation.Add pipelineStateDescriptor.colorAttachments[0].sourceRGBBlendFactor = MTLBlendFactor.SourceAlpha pipelineStateDescriptor.colorAttachments[0].sourceAlphaBlendFactor = MTLBlendFactor.SourceAlpha pipelineStateDescriptor.colorAttachments[0].destinationRGBBlendFactor = MTLBlendFactor.OneMinusSourceAlpha pipelineStateDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactor.OneMinusSourceAlpha let sampleDesc = MTLTextureDescriptor() sampleDesc.textureType = MTLTextureType.Type2DMultisample sampleDesc.width = inTexture.width sampleDesc.height = inTexture.height sampleDesc.sampleCount = 4 sampleDesc.pixelFormat = .RGBA8Unorm sampleDesc.storageMode = .Private sampleDesc.usage = .RenderTarget let sampletex = device.device.newTextureWithDescriptor(sampleDesc) let renderPassDescriptor = MTLRenderPassDescriptor() renderPassDescriptor.colorAttachments[0].texture = sampletex renderPassDescriptor.colorAttachments[0].resolveTexture = outTexture renderPassDescriptor.colorAttachments[0].loadAction = .Clear renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.0) renderPassDescriptor.colorAttachments[0].storeAction = .MultisampleResolve let renderCB = commandQueue.commandBuffer() let renderCommandEncoder = renderCB.renderCommandEncoderWithDescriptor(renderPassDescriptor) let pipelineState = try! device.device.newRenderPipelineStateWithDescriptor(pipelineStateDescriptor) renderCommandEncoder.setRenderPipelineState(pipelineState) let vertexBuf = device.device.newBufferWithLength(triangles.count * 3 * sizeof(VertexT), options: .CPUCacheModeDefaultCache) var vBufPointer = [VertexT]() for i in 0..<triangles.count { // create buffer here } memcpy(vertexBuf.contents(), &vBufPointer, triangles.count * 3 * sizeof(VertexT)) renderCommandEncoder.setVertexBuffer(vertexBuf, offset: 0, atIndex: 0) renderCommandEncoder.drawPrimitives(.Triangle, vertexStart: 0, vertexCount: triangles.count * 3) renderCommandEncoder.endEncoding() renderCB.commit() renderCB.waitUntilCompleted() 

You are now in the outTexture variable.