From 2361199267bf4a794a053c32f7e6bf54b215a0a1 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Sat, 3 Nov 2018 10:45:57 -0400
Subject: [PATCH] Add Terrain class that generates terrain

---
 Terrain.xcodeproj/project.pbxproj |  4 +++
 Terrain/Terrain.swift             | 48 +++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)
 create mode 100644 Terrain/Terrain.swift

diff --git a/Terrain.xcodeproj/project.pbxproj b/Terrain.xcodeproj/project.pbxproj
index 4b1ee0d..a987db7 100644
--- a/Terrain.xcodeproj/project.pbxproj
+++ b/Terrain.xcodeproj/project.pbxproj
@@ -13,6 +13,7 @@
 		C0C15A9D218DDDC3007494E2 /* TerrainViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = C0C15A9B218DDDC3007494E2 /* TerrainViewController.swift */; };
 		C0C15AA0218DE0B2007494E2 /* Renderer.swift in Sources */ = {isa = PBXBuildFile; fileRef = C0C15A9F218DE0B2007494E2 /* Renderer.swift */; };
 		C0C15AA2218DE21E007494E2 /* Math.swift in Sources */ = {isa = PBXBuildFile; fileRef = C0C15AA1218DE21E007494E2 /* Math.swift */; };
+		C0C15AA4218DE615007494E2 /* Terrain.swift in Sources */ = {isa = PBXBuildFile; fileRef = C0C15AA3218DE615007494E2 /* Terrain.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -25,6 +26,7 @@
 		C0C15A9B218DDDC3007494E2 /* TerrainViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TerrainViewController.swift; sourceTree = "<group>"; };
 		C0C15A9F218DE0B2007494E2 /* Renderer.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Renderer.swift; sourceTree = "<group>"; };
 		C0C15AA1218DE21E007494E2 /* Math.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Math.swift; sourceTree = "<group>"; };
+		C0C15AA3218DE615007494E2 /* Terrain.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Terrain.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -60,6 +62,7 @@
 				C0C15A8D218DDD85007494E2 /* AppDelegate.swift */,
 				C0C15A9B218DDDC3007494E2 /* TerrainViewController.swift */,
 				C0C15A9F218DE0B2007494E2 /* Renderer.swift */,
+				C0C15AA3218DE615007494E2 /* Terrain.swift */,
 				C0C15AA1218DE21E007494E2 /* Math.swift */,
 				C0C15A8F218DDD87007494E2 /* Assets.xcassets */,
 				C0C15A91218DDD87007494E2 /* MainMenu.xib */,
@@ -141,6 +144,7 @@
 			files = (
 				C0C15A9D218DDDC3007494E2 /* TerrainViewController.swift in Sources */,
 				C0C15AA0218DE0B2007494E2 /* Renderer.swift in Sources */,
+				C0C15AA4218DE615007494E2 /* Terrain.swift in Sources */,
 				C0C15A8E218DDD85007494E2 /* AppDelegate.swift in Sources */,
 				C0C15AA2218DE21E007494E2 /* Math.swift in Sources */,
 			);
diff --git a/Terrain/Terrain.swift b/Terrain/Terrain.swift
new file mode 100644
index 0000000..9ab5afa
--- /dev/null
+++ b/Terrain/Terrain.swift
@@ -0,0 +1,48 @@
+//
+//  Terrain.swift
+//  Terrain
+//
+//  Created by Eryn Wells on 11/3/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+import Cocoa
+
+class Terrain: NSObject {
+    override init() {
+        super.init()
+    }
+
+    /// Generate a grid of triangles and place the result in the given buffer.
+    /// @param buffer The buffer to copy the results into
+    /// @param size The size of the grid. Each square is a pair of triangles.
+    func generateVertexes(intoBuffer buffer: MTLBuffer, size: CGSize) {
+        let VertexesPerCell = 6
+
+        let float3Stride = MemoryLayout<Float3>.stride
+        let (width, height) = (Int(size.width), Int(size.height))
+        let expectedCount = VertexesPerCell * width * height
+        let expectedLength = float3Stride * expectedCount
+        guard buffer.length >= expectedLength else {
+            fatalError("Terrain.generateVertexes: buffer must be at least \(expectedLength) bytes to fix grid of size \(size)")
+        }
+
+        var vertexes = [Float3]()
+        vertexes.reserveCapacity(expectedCount)
+
+        let (cellWidth, cellHeight) = (Float(2.0) / Float(width), Float(2.0) / Float(height))
+        for y in 0..<Int(size.height) {
+            for x in 0..<Int(size.width) {
+                let base = VertexesPerCell * (y * width + x)
+                vertexes[base+0] = Float3(x: Float(x) * cellWidth, y: Float(y) * cellHeight, z: 0.0)
+                vertexes[base+1] = Float3(x: Float(x) * cellWidth, y: Float(y) * cellHeight + cellHeight, z: 0.0)
+                vertexes[base+2] = Float3(x: Float(x) * cellWidth + cellWidth, y: Float(y) * cellHeight, z: 0.0)
+                vertexes[base+3] = Float3(x: Float(x) * cellWidth + cellWidth, y: Float(y) * cellHeight, z: 0.0)
+                vertexes[base+4] = Float3(x: Float(x) * cellWidth, y: Float(y) * cellHeight + cellHeight, z: 0.0)
+                vertexes[base+5] = Float3(x: Float(x) * cellWidth + cellWidth, y: Float(y) * cellHeight + cellHeight, z: 0.0)
+            }
+        }
+
+        memcpy(buffer.contents(), vertexes, expectedLength)
+    }
+}