[Metaballs] A Metal graphics pipeline that builds and runs but crashes

Metaballs/Renderer.swift

@@ -7,3 +7,102 @@
 //
 
 import Foundation
+import MetaballsKit
+import MetalKit
+
+enum RendererError: Error {
+    case MetalError(String)
+}
+
+protocol RendererDelegate {
+    var renderSize: CGSize { get set }
+    var field: Field { get }
+}
+
+struct Vertex {
+    let x: Float
+    let y: Float
+    let texX: Float
+    let texY: Float
+}
+
+class Renderer: NSObject, MTKViewDelegate {
+    var delegate: RendererDelegate?
+
+    private var device: MTLDevice
+    private var commandQueue: MTLCommandQueue
+    private var renderPipelineState: MTLRenderPipelineState
+
+    init(view: MTKView, field: Field) throws {
+        guard let device = MTLCreateSystemDefaultDevice() else {
+            throw RendererError.MetalError("Unable to create Metal system device")
+        }
+        self.device = device
+        view.device = device
+        do {
+            try field.setupMetal(withDevice: device)
+        } catch let e {
+            throw e
+        }
+
+        let library = try device.makeDefaultLibrary(bundle: Bundle.main)
+        let vertexShader = library.makeFunction(name: "passthroughVertexShader")
+        let fragmentShader = library.makeFunction(name: "sampleToColorShader")
+
+        let pipelineStateDescriptor = MTLRenderPipelineDescriptor()
+        pipelineStateDescriptor.label = "Render Pipeline"
+        pipelineStateDescriptor.vertexFunction = vertexShader
+        pipelineStateDescriptor.fragmentFunction = fragmentShader
+        pipelineStateDescriptor.colorAttachments[0].pixelFormat = view.colorPixelFormat
+        renderPipelineState = try device.makeRenderPipelineState(descriptor: pipelineStateDescriptor)
+
+        commandQueue = device.makeCommandQueue()
+        super.init()
+    }
+
+    /// MARK: - MTKViewDelegate
+
+    func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
+        delegate?.renderSize = size
+        // TODO: Reallocate the sample buffer and texture
+    }
+
+    func draw(in view: MTKView) {
+        guard let field = delegate?.field else {
+            return
+        }
+
+        // Two triangles, plus texture coordinates.
+        let points: [Vertex] = [Vertex(x: 1, y: -1, texX: 1, texY: 0),
+                                Vertex(x: -1, y: -1, texX: 0, texY: 0),
+                                Vertex(x: -1, y: 1, texX: 0, texY: 1),
+
+                                Vertex(x: 1, y: -1, texX: 1, texY: 0),
+                                Vertex(x: -1, y: 1, texX: 0, texY: 1),
+                                Vertex(x: 1, y: 1, texX: 1, texY: 1)]
+
+        let buffer = commandQueue.makeCommandBuffer()
+        do {
+            let _ = try field.computeEncoderForSamplingKernel(withDevice: device, commandBuffer: buffer)
+            buffer.commit()
+        } catch let e {
+            print("\(e)")
+        }
+
+        if let renderPass = view.currentRenderPassDescriptor {
+            let encoder = buffer.makeRenderCommandEncoder(descriptor: renderPass)
+            encoder.label = "Render Pass"
+            encoder.setViewport(MTLViewport(originX: 0.0, originY: 0.0, width: Double(view.drawableSize.width), height: Double(view.drawableSize.height), znear: -1.0, zfar: 1.0))
+            encoder.setRenderPipelineState(renderPipelineState)
+            encoder.setVertexBytes(points, length: points.count * MemoryLayout<Vertex>.size, at: 0)
+            encoder.setFragmentTexture(field.sampleTexture, at: 0)
+            encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 6)
+            encoder.endEncoding()
+
+            if let drawable = view.currentDrawable {
+                buffer.present(drawable)
+            }
+        }
+        buffer.commit()
+    }
+}