initial lighting

Sources/Voxelotl/Renderer.swift

@@ -344,13 +344,16 @@ public class Renderer {
     assert(self._encoder != nil, "batch can't be called outside of a frame being rendered")
     assert(instances.count < 52)
 
-    var uniforms = ShaderUniforms(projView: camera.viewProjection)
+    var uniforms = ShaderUniforms(
+      projView: camera.viewProjection,
+      directionalLight: normalize(.init(0.75, -1, 0.5)))
     let instances = instances.map { (instance: Instance) -> ShaderInstance in
-      ShaderInstance(
-        model:
-          .translate(instance.position) *
-          matrix_float4x4(instance.rotation) *
-          .scale(instance.scale),
+      let model =
+        .translate(instance.position) *
+        matrix_float4x4(instance.rotation) *
+        .scale(instance.scale)
+      return ShaderInstance(
+        model: model, normalModel: model.inverse.transpose,
         color: SIMD4(Color<UInt8>(instance.color)))
     }
 
@@ -361,6 +364,9 @@ public class Renderer {
     self._encoder.setVertexBytes(&uniforms,
       length: MemoryLayout<ShaderUniforms>.stride,
       index: ShaderInputIdx.uniforms.rawValue)
+    self._encoder.setFragmentBytes(&uniforms,
+      length: MemoryLayout<ShaderUniforms>.stride,
+      index: ShaderInputIdx.uniforms.rawValue)
 
     self._encoder.drawIndexedPrimitives(
       type: .triangle,

Sources/Voxelotl/shader.metal

@@ -4,7 +4,7 @@
 
 struct FragmentInput {
   float4 position [[position]];
-  float4 normal;
+  float3 normal;
   float2 texCoord;
   half4 color;
 };
@@ -23,16 +23,24 @@ vertex FragmentInput vertexMain(
   FragmentInput out;
   out.position = ndc;
   out.color    = half4(i[instanceID].color) / 255.0;
-  out.normal   = vtx[vertexID].normal;
+  out.normal   = (i[instanceID].normalModel * vtx[vertexID].normal).xyz;
   out.texCoord = vtx[vertexID].texCoord;
   return out;
 }
 
 fragment half4 fragmentMain(
   FragmentInput in [[stage_in]],
-  metal::texture2d<half, metal::access::sample> texture [[texture(0)]]
+  metal::texture2d<half, metal::access::sample> texture [[texture(0)]],
+  constant ShaderUniforms& u [[buffer(ShaderInputIdxUniforms)]]
 ) {
   constexpr metal::sampler sampler(metal::address::repeat, metal::filter::nearest);
+  auto normal = metal::normalize(in.normal);
+
+  float lambert = metal::dot(normal, -u.directionalLight);
+  float diffuse = metal::max(0.0, lambert);
+
   half4 albedo = texture.sample(sampler, in.texCoord);
-  return albedo * in.color;
+  albedo *= in.color;
+
+  return albedo * diffuse;
 }

Sources/Voxelotl/shadertypes.h

@@ -24,11 +24,13 @@ typedef struct {
 
 typedef struct {
   matrix_float4x4 model;
+  matrix_float4x4 normalModel;
   vector_uchar4 color;
 } ShaderInstance;
 
 typedef struct {
   matrix_float4x4 projView;
+  vector_float3 directionalLight;
 } ShaderUniforms;
 
 #endif//SHADERTYPES_H