debug: simple diffuse point light — test if light data reaches fragment

src/Engine.Graphics.Vulkan/Shaders/triangle.frag

@@ -14,6 +14,17 @@ layout(set = 0, binding = 0) uniform CameraUBO {
 
 void main()
 {
-    // Just output albedo — tests if vp matrix in 128B UBO works
-    outColor = vec4(fragAlbedo, 1.0);
+    vec3 N = normalize(fragNormal);
+    vec3 toLight = pointLightPos.xyz - fragWorldPos;
+    float dist = length(toLight);
+    vec3 L = normalize(toLight);
+
+    float NdotL = max(dot(N, L), 0.0);
+    float atten = 1.0 / (1.0 + dist * dist * 0.05);
+    float intensity = pointLightPos.w;
+
+    vec3 color = fragAlbedo * pointLightColor.xyz * NdotL * intensity * atten;
+    color += fragAlbedo * 0.02;
+
+    outColor = vec4(color, 1.0);
 }