From 256969454f407860ff453a1402feb0769817a3c5 Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Tue, 7 Apr 2026 18:54:28 -0500
Subject: [PATCH] phong lighting

---
 shader/triangle.hlsl | 37 +++++++++++++++++++++++++------------
 src/main.cpp         | 22 +++++++++++++---------
 2 files changed, 38 insertions(+), 21 deletions(-)

diff --git a/shader/triangle.hlsl b/shader/triangle.hlsl
index eea69e3..a9b7139 100644
--- a/shader/triangle.hlsl
+++ b/shader/triangle.hlsl
@@ -10,15 +10,16 @@ struct VSOutput
   float4 Position : SV_POSITION;
   float3 Normal : NORMAL0;
   float2 Texture : TEXCOORD0;
+  float3 LightDirection : NORMAL1;
+  float3 ViewDirection : NORMAL2;
 };
 
 struct ShaderData
 {
-  float4x4 Projection;
-  float4x4 View;
-  float4x4 Model;
-  float4 lightPosition;
-  uint32_t selected;
+  float4x4 Transform;
+  float4x4 ModelView;
+  float4 LightPosition; // view space
+  uint32_t Selected;
 };
 
 struct PushConstant {
@@ -35,10 +36,14 @@ struct PushConstant constants;
 VSOutput VSMain(VSInput input)
 {
   VSOutput output = (VSOutput)0;
-  output.Position = mul(constants.data.Get().Projection, mul(constants.data.Get().View, mul(constants.data.Get().Model, float4(input.Position.xyz, 1.0))));
-  //output.Normal = mul((float3x3)constants.data.Get().Model, input.Normal);
-  output.Normal = input.Normal * 0.5 + 0.5;
+  output.Position = mul(constants.data.Get().Transform, float4(input.Position.xyz, 1.0));
+  output.Normal = mul((float3x3)constants.data.Get().ModelView, input.Normal);
   output.Texture = input.Texture.xy;
+
+  float4 viewPosition = mul(constants.data.Get().ModelView, float4(input.Position.xyz, 1.0));
+  output.LightDirection = (constants.data.Get().LightPosition - viewPosition).xyz;
+  output.ViewDirection = -viewPosition.xyz;
+
   return output;
 }
 
@@ -47,13 +52,22 @@ float4 PSMain(VSOutput input) : SV_TARGET
 {
   float3 color = textures[0].Sample(samplers[0], input.Texture).bgr;
 
-  return float4(color, 1.0);
+  float3 N = normalize(input.Normal);
+  float3 L = normalize(input.LightDirection);
+  float3 V = normalize(input.ViewDirection);
+  float3 R = reflect(-L, N);
+
+  const float a = 16.0;
+  const float specularIntensity = 0.8;
+  float3 specular = pow(max(dot(R, V), 0), a) * specularIntensity;
+  float3 diffuse = max(dot(N, L), 0.001);
+
+  return float4(diffuse * color + specular, 1.0);
 }
 
 struct VSOutlineOutput
 {
   float4 Position : SV_POSITION;
-  float3 Normal : NORMAL0;
 };
 
 [shader("vertex")]
@@ -61,8 +75,7 @@ VSOutlineOutput VSOutlineMain(VSInput input)
 {
   VSOutlineOutput output = (VSOutlineOutput)0;
   float3 position = input.Position.xyz + input.Normal.xyz * 0.01;
-  output.Position = mul(constants.data.Get().Projection, mul(constants.data.Get().View, mul(constants.data.Get().Model, float4(position, 1.0))));
-  output.Normal = input.Normal;
+  output.Position = mul(constants.data.Get().Transform, float4(position, 1.0));
   return output;
 }
 
diff --git a/src/main.cpp b/src/main.cpp
index 27ffe21..dad2b8b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -129,12 +129,10 @@ VkDescriptorSet textureDescriptorSet{ VK_NULL_HANDLE };
 XMINT2 windowSize{};
 
 struct ShaderData {
-  XMFLOAT4X4 projection;
-  XMFLOAT4X4 view;
-  XMFLOAT4X4 model;
-  //XMFLOAT4X4 model[3];
-  XMFLOAT4 lightPosition{ 0.0f, -10.0f, 10.0f, 0.0f };
-  uint32_t selected{ 1 };
+  XMFLOAT4X4 transform;
+  XMFLOAT4X4 modelView;
+  XMFLOAT4 lightPosition;
+  uint32_t selected;
 };
 
 ShaderData shaderData{};
@@ -1191,9 +1189,15 @@ int main()
     VK_CHECK_SWAPCHAIN(vkAcquireNextImageKHR(device, swapchain, UINT64_MAX, presentSemaphores[frameIndex], VK_NULL_HANDLE, &imageIndex));
 
     // shader data
-    XMStoreFloat4x4(&shaderData.projection, currentProjection());
-    XMStoreFloat4x4(&shaderData.view, currentView());
-    XMStoreFloat4x4(&shaderData.model, currentModel());
+    XMMATRIX model = currentModel();
+    XMMATRIX view = currentView();
+    XMMATRIX modelView = model * view;
+    XMMATRIX transform = modelView * currentProjection();
+    XMStoreFloat4x4(&shaderData.transform, transform);
+    XMStoreFloat4x4(&shaderData.modelView, modelView);
+    XMVECTOR lightPosition = XMVector3Transform(XMVectorSet(-3, -3, 0, 0), view);
+    XMStoreFloat4(&shaderData.lightPosition, lightPosition);
+
     size_t frameOffset = shaderDataDevice.stride * frameIndex;
     void * frameData = (void *)(((VkDeviceSize)shaderDataDevice.mappedData) + frameOffset);
     VkDeviceSize frameSize{ (sizeof (ShaderData)) };