[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()
+    }
+}

Metaballs/Shaders.metal

@@ -9,16 +9,10 @@
 #include <metal_stdlib>
 using namespace metal;
 
-typedef struct {
-    float2 position;
-    float radius;
-} Ball;
-
-
 typedef struct {
     float2 position;
     float2 textureCoordinate;
-} VertexIn;
+} Vertex;
 
 // From HelloCompute sample code project.
 // Vertex shader outputs and per-fragmeht inputs. Includes clip-space position and vertex outputs interpolated by rasterizer and fed to each fragment genterated by clip-space primitives.
@@ -30,22 +24,26 @@ typedef struct {
     float2 textureCoordinate;
 } RasterizerData;
 
-//vertex RasterizerData
-//passthroughVertexShader(uint vertexID [[vertex_id]])
-//{
-//    // TODO: Nothing really. Just pass on through to the fragment shader.
-//}
+vertex RasterizerData
+passthroughVertexShader(uint vid                    [[vertex_id]],
+                        constant Vertex* vertexes   [[buffer(0)]])
+{
+    RasterizerData out;
+    Vertex v = vertexes[vid];
+    out.position = float4(v.position.xy, 0.0, 1.0);
+    out.textureCoordinate = v.textureCoordinate;
+    return out;
+}
 
 fragment float4
-sampleToColorShader(RasterizerData in       [[stage_in]],
-                    constant float* samples [[buffer(0)]],
-                    constant float2* size   [[buffer(1)]])
+sampleToColorShader(RasterizerData in           [[stage_in]],
+                    texture2d<half> samples     [[texture(0)]])
 {
-    int index = in.textureCoordinate.y * size->y + in.textureCoordinate.x;
-    float sample = samples[index];
+    constexpr sampler textureSampler(mag_filter::linear, min_filter::linear);
+    const half4 sample = samples.sample(textureSampler, in.textureCoordinate);
 
     float4 out;
-    if (sample > 1.0) {
+    if (sample.r > 1.0) {
         out = float4(0.0, 1.0, 0.0, 0.0);
     }
     else {