Read texture data from the heights texture

Terrain2/Shaders.metal

@@ -30,12 +30,17 @@ typedef struct
 } ColorInOut;
 
 vertex ColorInOut vertexShader(Vertex in [[stage_in]],
-                               texture2d<half> heights [[ texture(1) ]],
-                               constant Uniforms & uniforms [[ buffer(BufferIndexUniforms) ]])
+                               texture2d<half> heights [[texture(0)]],
+                               constant Uniforms & uniforms [[buffer(BufferIndexUniforms)]])
 {
+    constexpr sampler s(coord::pixel, address::clamp_to_zero, filter::linear);
+
     ColorInOut out;
 
-    float4 position = float4(in.position, 1.0);
+    uint2 gridCoord(in.texCoord.x * heights.get_width(), in.texCoord.y * heights.get_height());
+    half4 height = heights.read(gridCoord).rrrr;
+
+    float4 position(in.position.x, float(height.r), in.position.z, 1.0);
     out.position = uniforms.projectionMatrix * uniforms.modelViewMatrix * position;
     out.texCoord = in.texCoord;
 

Terrain2/Terrain.swift

@@ -43,10 +43,11 @@ class Terrain: NSObject {
     }
 
     /// Create and condition mesh data to feed into a pipeline using the given vertex descriptor.
-    /// @param dimensions Coordinate dimensions of the plane
-    /// @param segments Number of segments to divide each dimension into
-    /// @param device Metal device
-    /// @param vertexDescriptor Description of how to lay out vertex data in GPU memory
+    ///
+    /// - parameter dimensions: Coordinate dimensions of the plane.
+    /// - parameter segments: Number of segments to divide each dimension into.
+    /// - parameter device: Metal device.
+    /// - parameter vertexDescriptor: Description of how to lay out vertex data in GPU memory.
     class func buildMesh(withDimensions dimensions: float2, segments: uint2, device: MTLDevice, vertexDescriptor: MTLVertexDescriptor) throws -> MTKMesh {
         let metalAllocator = MTKMeshBufferAllocator(device: device)