Support lighting using a graphics buffer that is kep open!

Assets/source/SolidColor.frag.hlsl

@@ -1,10 +1,46 @@
 #include "RootConstants.hlsl"
 
-float4 main(float4 Color : TEXCOORD0, float3 WorldNormal : TEXCOORD1) : SV_Target0
+struct Input
 {
-    float3 N = normalize(WorldNormal);
-    float  NdotL = saturate(dot(N, -LightDirection));
-    float3 diffuse = Color.rgb * LightColor * NdotL;
-    float3 ambient = Color.rgb * AmbientIntensity;
-    return float4(diffuse + ambient, Color.a);
+    float4 Color         : TEXCOORD0;
+    float3 WorldNormal   : TEXCOORD1;
+    float3 WorldPosition : TEXCOORD2;
+};
+
+float4 main(Input input) : SV_Target0
+{
+    float3 normal = normalize(input.WorldNormal);
+
+    // Initial ambient component
+    float3 result = input.Color.rgb * LightColor * AmbientIntensity;
+
+    // Directional light contribution
+    float ndotl = max(dot(normal, -LightDirection), 0.0);
+    result += input.Color.rgb * LightColor * ndotl;
+
+    // Point lights
+    if (ActiveLightCount > 0)
+    {
+        StructuredBuffer<PointLight> pointLights = ResourceDescriptorHeap[LightBufferIndex];
+        
+        for (uint i = 0; i < ActiveLightCount; ++i)
+        {
+            PointLight light = pointLights[i];
+
+            float3 lightDir = light.Position - input.WorldPosition;
+            float  dist     = length(lightDir);
+            
+            if (dist < light.Radius)
+            {
+                lightDir = normalize(lightDir);
+                float attenuation = 1.0 - (dist / light.Radius);
+                attenuation = max(attenuation, 0.0);
+
+                float pndotl = max(dot(normal, lightDir), 0.0);
+                result += light.Color * input.Color.rgb * pndotl * attenuation * light.Intensity;
+            }
+        }
+    }
+
+    return float4(result, input.Color.a);
 }