Eliminates the quad buffer.

Vertices can be adduced from vertex ID.

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -5169,6 +5169,7 @@
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.11;
 				MTL_ENABLE_DEBUG_INFO = INCLUDE_SOURCE;
+				MTL_FAST_MATH = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = macosx;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
@@ -5220,6 +5221,7 @@
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.11;
 				MTL_ENABLE_DEBUG_INFO = NO;
+				MTL_FAST_MATH = YES;
 				SDKROOT = macosx;
 				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
 				SWIFT_SWIFT3_OBJC_INFERENCE = Default;

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm

@@ -31,7 +31,6 @@ constexpr size_t NumBufferedScans = 2048;
 	id<MTLRenderPipelineState> _gouraudPipeline;
 
 	// Buffers.
-	id<MTLBuffer> _quadBuffer;		// i.e. four vertices defining a quad.
 	id<MTLBuffer> _uniformsBuffer;
 	id<MTLBuffer> _scansBuffer;
 
@@ -44,15 +43,6 @@ constexpr size_t NumBufferedScans = 2048;
 	if(self) {
 		_commandQueue = [view.device newCommandQueue];
 
-		// Install the standard quad.
-		constexpr float vertices[] = {
-			0.0f,	0.0f,
-			0.0f,	1.0f,
-			1.0f,	0.0f,
-			1.0f,	1.0f,
-		};
-		_quadBuffer = [view.device newBufferWithBytes:vertices length:sizeof(vertices) options:MTLResourceCPUCacheModeDefaultCache];
-
 		// Allocate space for uniforms.
 		_uniformsBuffer = [view.device newBufferWithLength:16 options:MTLResourceCPUCacheModeWriteCombined];
 		_uniforms.scale[0] = 1024;
@@ -67,22 +57,12 @@ constexpr size_t NumBufferedScans = 2048;
 			options:MTLResourceCPUCacheModeWriteCombined | MTLResourceStorageModeShared];
 		[self setTestScans];
 
-		// The quad buffer has only 2d positions; the scan buffer is a bit more complicated
-		MTLVertexDescriptor *vertexDescriptor = [[MTLVertexDescriptor alloc] init];
-		vertexDescriptor.attributes[0].bufferIndex = 0;
-		vertexDescriptor.attributes[0].offset = 0;
-		vertexDescriptor.attributes[0].format = MTLVertexFormatFloat2;
-		vertexDescriptor.layouts[0].stride = sizeof(float)*2;
-
-		// TODO: shouldn't I need to explain the Scan layout, too? Or do these things not need to be specified when compatible?
-
 		// Generate TEST pipeline.
 		id<MTLLibrary> library = [view.device newDefaultLibrary];
 		MTLRenderPipelineDescriptor *pipelineDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
 		pipelineDescriptor.vertexFunction = [library newFunctionWithName:@"scanVertexMain"];
 		pipelineDescriptor.fragmentFunction = [library newFunctionWithName:@"scanFragmentMain"];
 		pipelineDescriptor.colorAttachments[0].pixelFormat = view.colorPixelFormat;
-		pipelineDescriptor.vertexDescriptor = vertexDescriptor;
 		_gouraudPipeline = [view.device newRenderPipelineStateWithDescriptor:pipelineDescriptor error:nil];
 	}
 
@@ -134,9 +114,8 @@ constexpr size_t NumBufferedScans = 2048;
 	// Drawing. Just the test triangle, as described above.
 	[encoder setRenderPipelineState:_gouraudPipeline];
 
-	[encoder setVertexBuffer:_quadBuffer offset:0 atIndex:0];
+	[encoder setVertexBuffer:_scansBuffer offset:0 atIndex:0];
 	[encoder setVertexBuffer:_uniformsBuffer offset:0 atIndex:1];
-	[encoder setVertexBuffer:_scansBuffer offset:0 atIndex:2];
 
 	[encoder drawPrimitives:MTLPrimitiveTypeTriangleStrip vertexStart:0 vertexCount:4 instanceCount:2];
 

OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal

@@ -9,9 +9,6 @@
 #include <metal_stdlib>
 using namespace metal;
 
-// These two structs are the same, but defined separately as an artefact
-// of my learning process, and the fact that they soon won't be.
-
 struct Uniforms {
 	// This is used to scale scan positions, i.e. it provides the range
 	// for mapping from scan-style integer positions into eye space.
@@ -40,11 +37,6 @@ struct Scan {
 	uint32_t dataYAndLine			[[attribute(7)]];
 };
 
-// This is a custom thing defining one corner of a quad.
-struct QuadInputVertex {
-	float2 position	[[attribute(0)]];
-};
-
 struct ColouredVertex {
 	float4 position [[position]];
 };
@@ -52,28 +44,28 @@ struct ColouredVertex {
 
 // MARK: - Scan shaders; these do final output to the display.
 
-vertex ColouredVertex scanVertexMain(	QuadInputVertex vert [[stage_in]],
+vertex ColouredVertex scanVertexMain(	constant Uniforms &uniforms [[buffer(1)]],
-										constant Uniforms &uniforms [[buffer(1)]],
+										constant Scan *scans [[buffer(0)]],
-										constant Scan *scans [[buffer(2)]],
+										uint instanceID [[instance_id]],
-										ushort instance [[instance_id]]) {
+										uint vertexID [[vertex_id]]) {
 	// Unpack start and end vertices; little-endian numbers are assumed here.
 	const float2 start = float2(
-		float(scans[instance].startPosition & 0xffff) / float(uniforms.scale.x),
+		float(scans[instanceID].startPosition & 0xffff) / float(uniforms.scale.x),
-		float(scans[instance].startPosition >> 16) / float(uniforms.scale.y)
+		float(scans[instanceID].startPosition >> 16) / float(uniforms.scale.y)
 	);
 	const float2 end = float2(
-		float(scans[instance].endPosition & 0xffff) / float(uniforms.scale.x),
+		float(scans[instanceID].endPosition & 0xffff) / float(uniforms.scale.x),
-		float(scans[instance].endPosition >> 16) / float(uniforms.scale.y)
+		float(scans[instanceID].endPosition >> 16) / float(uniforms.scale.y)
 	);
 
 	// Calculate the tangent and normal.
-	const float2 tangent = end - start;
+	const float2 tangent = (end - start);
 	const float2 normal = float2(-tangent.y, tangent.x) / length(tangent);
 
 	// Hence determine this quad's real shape.
 	ColouredVertex output;
 	output.position = float4(
-		((start + vert.position.x * tangent + vert.position.y * normal * uniforms.lineWidth) * float2(2.0, -2.0) + float2(-1.0, 1.0)) * float2(uniforms.aspectRatioMultiplier, 1.0),
+		((start + (float(vertexID&2) * 0.5) * tangent + (float(vertexID&1) - 0.5) * normal * uniforms.lineWidth) * float2(2.0, -2.0) + float2(-1.0, 1.0)) * float2(uniforms.aspectRatioMultiplier, 1.0),
 		0.0,
 		1.0
 	);