From 4c560602604db40542b4c4beff9259025e882f94 Mon Sep 17 00:00:00 2001
From: Anish Bhobe <anishbhobe@hotmail.com>
Date: Wed, 2 Jul 2025 15:54:11 +0200
Subject: [PATCH] Integrated Directional Light.

---
 Blaze/Assets/Shaders/Mesh.slang | 60 ++++++++++++++++++++++++---------
 Blaze/Source/Blaze.cpp          | 11 ++++++
 2 files changed, 56 insertions(+), 15 deletions(-)

diff --git a/Blaze/Assets/Shaders/Mesh.slang b/Blaze/Assets/Shaders/Mesh.slang
index e3ac5b6..f20dd64 100644
--- a/Blaze/Assets/Shaders/Mesh.slang
+++ b/Blaze/Assets/Shaders/Mesh.slang
@@ -202,6 +202,46 @@ float3 GetPointLightInfluence(float3 Albedo, float2 MetalRough, float3 Position,
     return Contrib;
 }
 
+float3 GetDirectionalLightInfluence(float3 Albedo, float2 MetalRough, float3 Position, float3 Normal)
+{
+    if (pfd.lightData.dirLightCount == 0)
+        return 0.0f.xxx;
+    
+    float3 ViewDir = normalize(pfd.camera.position.xyz - Position);
+    
+    float Metallic = MetalRough.r;
+    float Roughness = MetalRough.g;
+    
+    // Dielectric F_0 based on LearnOpenGL.
+    // TODO: Cite    
+    float3 F_0 = 0.04f.xxx;
+    F_0 = lerp(F_0, Albedo, Metallic);
+    
+    float3 Contrib = 0.0f;
+    for (uint i = 0; i < pfd.lightData.dirLightCount; ++i)
+    {
+        DirectionalLight Light = pfd.lightData.dirLights[i];
+        
+        if (Light._padding0 < 0.0f)
+            continue;
+        
+        float3 LightDir = -normalize(Light.direction);
+        
+        // Color Unpack
+        //float R = (Light.Color & 0xFF000000) >> 24;
+        //float G = (Light.Color & 0x00FF0000) >> 16;
+        //float B = (Light.Color & 0x0000FF00) >> 8;
+        
+        //float3 LightColor = Light.Intensity * float3(R, G, B) * 0.00392156862f; // 0.00392156862 = 1/255
+
+        float3 LightColor = Light.color;
+ 
+        Contrib += GetPBRContrib(Albedo, LightColor, ViewDir, Normal, Metallic, Roughness, F_0, LightDir, 1.0f);
+    }
+    
+    return Contrib;
+}
+
 [shader("fragment")]
 float4 FragmentMain(
     float4 position         : POSITION,
@@ -215,22 +255,12 @@ float4 FragmentMain(
     float3 N = pcb.material.getNormal(position.xyz, normal.xyz, tangent, texCoord0);
     float2 metalRough = pcb.material.getMetalRough(texCoord0);
 
-    let albedo = pcb.material.getAlbedo(texCoord0, vertexColor0);
-    let viewDir = normalize(position.xyz - pfd.camera.position.xyz);
+    float4 albedo = pcb.material.getAlbedo(texCoord0, vertexColor0);
+    float3 viewDir = normalize(position.xyz - pfd.camera.position.xyz);
 
-    //float3 f_0 = 0.04f.xxx;
-    //f_0 = lerp(f_0, albedo.rgb, metalRough.x);
+    float3 pointContrib = GetPointLightInfluence(albedo.rgb, metalRough, position.xyz, N);
+    float3 dirContrib = GetDirectionalLightInfluence(albedo.rgb, metalRough, position.xyz, N);
 
-
-    //float3 contrib = 0.0f.xxx;
-    //for (uint i = 0; i < pfd.lightData.pointLightCount; ++i) {
-    //    PointLight pointlight = pfd.lightData.pointLights[i];
-
-    //    contrib += pointlight.getInfluence(albedo.rgb, metalRough, viewDir, position.xyz, N, f_0);
-    //}
-
-    let contrib = GetPointLightInfluence(albedo.rgb, metalRough, position.xyz, N);
-
-    return float4(pcb.material.getEmissive(texCoord0) + contrib, 1.0f);
+    return float4(pcb.material.getEmissive(texCoord0) + pointContrib + dirContrib, 1.0f);
 }
 
diff --git a/Blaze/Source/Blaze.cpp b/Blaze/Source/Blaze.cpp
index 9c338f2..6391f27 100644
--- a/Blaze/Source/Blaze.cpp
+++ b/Blaze/Source/Blaze.cpp
@@ -76,6 +76,17 @@ SDL_AppResult SDL_AppInit( void** appstate, int, char** )
 
   app_state.renderDevice->bufferManager->WriteToBuffer( app_state.miscData->pointLights, point_light );
 
+  Blaze::MiscData::DirectionalLight dir_light[] = {
+    {
+     .direction = { 1.0f, -1.0f, 0.0f },
+     .color     = { 12.0f, 10.0f, 5.0f },
+     },
+  };
+
+  app_state.miscData->lightData.dirLightCount = _countof( dir_light );
+
+  app_state.renderDevice->bufferManager->WriteToBuffer( app_state.miscData->directionalLights, dir_light );
+
   memcpy(
     app_state.miscData->cameraUniformBufferPtr + sizeof( Blaze::MiscData::CameraData ),
     &app_state.miscData->lightData,