From 1ed5f0bf6e90b0f1426eb22624075582b29c7212 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Fri, 12 Oct 2018 17:15:33 -0700
Subject: [PATCH] Orthographic projectify the vertexes

---
 MetaballsKit/Renderer.swift | 19 ++++++++++++++++++-
 MetaballsKit/Shaders.metal  | 11 ++++++++---
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/MetaballsKit/Renderer.swift b/MetaballsKit/Renderer.swift
index bbd7f96..d58a5c2 100644
--- a/MetaballsKit/Renderer.swift
+++ b/MetaballsKit/Renderer.swift
@@ -19,6 +19,10 @@ public protocol RendererDelegate {
     var metalView: MTKView { get }
 }
 
+private struct RenderParameters {
+    var projection: Matrix4x4
+}
+
 struct Vertex {
     let position: Float2
     let textureCoordinate: Float2
@@ -52,6 +56,8 @@ public class Renderer: NSObject, MTKViewDelegate {
     private var pixelPipeline: MTLRenderPipelineState?
     private var marchingSquaresPipeline: MTLRenderPipelineState?
 
+    private var parametersBuffer: MTLBuffer?
+
     override public init() {
         guard let device = MTLCreateSystemDefaultDevice() else {
             fatalError("Unable to create Metal system device")
@@ -63,6 +69,9 @@ public class Renderer: NSObject, MTKViewDelegate {
         self.device = device
         commandQueue = queue
 
+        let parametersLength = MemoryLayout<RenderParameters>.size
+        parametersBuffer = device.makeBuffer(length: parametersLength, options: .storageModeShared)
+
         super.init()
     }
 
@@ -143,6 +152,13 @@ public class Renderer: NSObject, MTKViewDelegate {
 
     public func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
         delegate?.renderSize = Size(size: size)
+
+        if let buffer = parametersBuffer {
+            let aspectRatio = Float(size.width / size.height)
+            let projectionMatrix = Matrix4x4.orthographicProjection(top: 1.0, left: -aspectRatio, bottom: -1.0, right: aspectRatio, near: 0.0, far: 1.0)
+            let params = RenderParameters(projection: projectionMatrix)
+            memcpy(buffer.contents(), [params], MemoryLayout<RenderParameters>.size)
+        }
     }
 
     public func draw(in view: MTKView) {
@@ -172,9 +188,9 @@ public class Renderer: NSObject, MTKViewDelegate {
             if let pipeline = pixelPipeline,
                let encoder = buffer.makeRenderCommandEncoder(descriptor: renderPass) {
                 encoder.label = "Pixel Render"
-                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(pipeline)
                 encoder.setVertexBytes(points, length: points.count * MemoryLayout<Vertex>.stride, index: 0)
+                encoder.setVertexBuffer(parametersBuffer, offset: 0, index: 1)
                 encoder.setFragmentBuffer(field.parametersBuffer, offset: 0, index: 0)
                 encoder.setFragmentBuffer(field.ballBuffer, offset: 0, index: 1)
                 encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 6)
@@ -191,6 +207,7 @@ public class Renderer: NSObject, MTKViewDelegate {
                 encoder.label = "Marching Squares Render"
                 encoder.setRenderPipelineState(pipeline)
                 encoder.setVertexBytes(points, length: points.count * MemoryLayout<Vertex>.stride, index: 0)
+                encoder.setVertexBuffer(parametersBuffer, offset: 0, index: 1)
                 encoder.setTriangleFillMode(.lines)
                 encoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 6)
                 encoder.endEncoding()
diff --git a/MetaballsKit/Shaders.metal b/MetaballsKit/Shaders.metal
index 48b7c03..95cebc2 100644
--- a/MetaballsKit/Shaders.metal
+++ b/MetaballsKit/Shaders.metal
@@ -43,17 +43,22 @@ typedef struct {
     float3x3 colorTransform;
 } Parameters;
 
+struct RenderParameters {
+    float4x4 projection;
+};
+
 typedef float3 Ball;
 
 #pragma mark - Vertex
 
 vertex RasterizerData
-passthroughVertexShader(uint vid                    [[vertex_id]],
-                        constant Vertex* vertexes   [[buffer(0)]])
+passthroughVertexShader(uint vid [[vertex_id]],
+                        constant Vertex* vertexes [[buffer(0)]],
+                        constant RenderParameters &renderParameters [[buffer(1)]])
 {
     RasterizerData out;
     Vertex v = vertexes[vid];
-    out.position = float4(v.position.xy, 0.0, 1.0);
+    out.position = renderParameters.projection * float4(v.position.xy, 0.0, 1.0);
     out.textureCoordinate = v.textureCoordinate;
     return out;
 }