Extract Terrain into its own class

Terrain2/Terrain.swift

@@ -0,0 +1,79 @@
+//
+//  Terrain.swift
+//  Terrain
+//
+//  Created by Eryn Wells on 11/3/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+import Cocoa
+import MetalKit
+
+class Terrain: NSObject {
+
+    /// Creete a Metal vertex descriptor specifying how vertices will by laid out for input into our render pipeline and how we'll layout our Model IO vertices.
+    class func buildVertexDescriptor() -> MTLVertexDescriptor {
+        let mtlVertexDescriptor = MTLVertexDescriptor()
+
+        mtlVertexDescriptor.attributes[VertexAttribute.position.rawValue].format = MTLVertexFormat.float3
+        mtlVertexDescriptor.attributes[VertexAttribute.position.rawValue].offset = 0
+        mtlVertexDescriptor.attributes[VertexAttribute.position.rawValue].bufferIndex = BufferIndex.meshPositions.rawValue
+
+        mtlVertexDescriptor.attributes[VertexAttribute.texcoord.rawValue].format = MTLVertexFormat.float2
+        mtlVertexDescriptor.attributes[VertexAttribute.texcoord.rawValue].offset = 0
+        mtlVertexDescriptor.attributes[VertexAttribute.texcoord.rawValue].bufferIndex = BufferIndex.meshGenerics.rawValue
+
+        mtlVertexDescriptor.layouts[BufferIndex.meshPositions.rawValue].stride = 12
+        mtlVertexDescriptor.layouts[BufferIndex.meshPositions.rawValue].stepRate = 1
+        mtlVertexDescriptor.layouts[BufferIndex.meshPositions.rawValue].stepFunction = MTLVertexStepFunction.perVertex
+
+        mtlVertexDescriptor.layouts[BufferIndex.meshGenerics.rawValue].stride = 8
+        mtlVertexDescriptor.layouts[BufferIndex.meshGenerics.rawValue].stepRate = 1
+        mtlVertexDescriptor.layouts[BufferIndex.meshGenerics.rawValue].stepFunction = MTLVertexStepFunction.perVertex
+
+        return mtlVertexDescriptor
+    }
+
+    /// Create and condition mesh data to feed into a pipeline using the given vertex descriptor.
+    class func buildMesh(withDimensions dimensions: float2, segments: uint2, device: MTLDevice, vertexDescriptor: MTLVertexDescriptor) throws -> MTKMesh {
+        let metalAllocator = MTKMeshBufferAllocator(device: device)
+
+        let plane = MDLMesh.newPlane(withDimensions: dimensions,
+                                     segments: segments,
+                                     geometryType: .triangles,
+                                     allocator: metalAllocator)
+
+        let mdlVertexDescriptor = MTKModelIOVertexDescriptorFromMetal(vertexDescriptor)
+
+        guard let attributes = mdlVertexDescriptor.attributes as? [MDLVertexAttribute] else {
+            throw RendererError.badVertexDescriptor
+        }
+        attributes[VertexAttribute.position.rawValue].name = MDLVertexAttributePosition
+        attributes[VertexAttribute.texcoord.rawValue].name = MDLVertexAttributeTextureCoordinate
+
+        plane.vertexDescriptor = mdlVertexDescriptor
+
+        return try MTKMesh(mesh:plane, device:device)
+    }
+
+    let dimensions: float2
+    let segments: uint2
+
+    let vertexDescriptor: MTLVertexDescriptor
+    let mesh: MTKMesh
+
+    init?(dimensions dim: float2, segments seg: uint2, device: MTLDevice) {
+        dimensions = dim
+        segments = seg
+        vertexDescriptor = Terrain.buildVertexDescriptor()
+
+        do {
+            mesh = try Terrain.buildMesh(withDimensions: dimensions, segments: segments, device: device, vertexDescriptor: vertexDescriptor)
+        } catch let e {
+            print("Couldn't create mesh. Error: \(e)")
+            return nil
+        }
+
+        super.init()
+    }
+}