From 6f5c094f49fce3a9bc11098cfdc4a1763be017e2 Mon Sep 17 00:00:00 2001
From: Abdelrahman <said.abdelrahman89@gmail.com>
Date: Sat, 24 Aug 2024 00:25:41 +0100
Subject: [PATCH] Use matrices to transform light and normals

---
 src/shader/shaders.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/shader/shaders.c b/src/shader/shaders.c
index 51289d1..0351f04 100644
--- a/src/shader/shaders.c
+++ b/src/shader/shaders.c
@@ -25,7 +25,7 @@ internal V3f g_ambient_light = {0.3f, 0.75f, 0.15f};
 internal DirectionalLight g_directional_light = {
     .diffuse_intensity = {0.9f, 0.8f, 0.6f},
     .specular_intensity = {0.5f, 0.8f, 2.0f},
-    .direction = {0.0f, 0.0f, 1.0f},
+    .direction = {0.0f, 0.0f, 1.4f},
 };
 internal V3f g_eye = {0.2f, 0.1f, 0.75f};
 internal V3f g_target = {0};
@@ -88,18 +88,33 @@ internal FragmentResult phong_shader_fragment(void *shader,
                                               const FragmentData *data,
                                               const Colour *colour,
                                               const Model *model) {
+  Shader *shader_ptr = (Shader *)shader;
+
+  V4f hnorm;
   V3f norm;
   if (model->normal) {
     u64 nm_x = data->tex_coords.u * model->normal->width;
     u64 nm_y = (1.0f - data->tex_coords.v) * model->normal->height;
 
     Colour pixel = get_pixel(Colour, model->normal, nm_x, nm_y);
-    norm = (V3f){.x = pixel.r, .y = pixel.g, .z = pixel.b};
-    normalise_v3(norm);
+    hnorm = (V4f){
+        .x = pixel.r,
+        .y = pixel.g,
+        .z = pixel.b,
+        .w = 1.0f,
+    };
   } else {
-    norm = data->normal;
+    hnorm = V3_to_V4(data->normal);
   }
 
+  M4x4f matrix = mat4x4_mul(shader_ptr->projection, shader_ptr->model_view);
+  M4x4f transposed = mat4x4_transpose(matrix);
+  M4x4f inv_transpose = mat4x4_inv(transposed);
+
+  hnorm = mat4x4_mul_vec4(inv_transpose, hnorm);
+  norm = project_vec4(hnorm);
+  normalise_v3(norm);
+
   Colour output;
   if (model->texture) {
     u64 tx_x = data->tex_coords.u * model->texture->width;
@@ -115,8 +130,12 @@ internal FragmentResult phong_shader_fragment(void *shader,
   // Ambient term
   V3f intensity = num_mul_v3(g_ambient_light, model->material.ambient);
 
+  V4f hdir = V3_to_V4(g_directional_light.direction);
+  hdir = mat4x4_mul_vec4(matrix, hdir);
+  V3f light_dir = project_vec4(hdir);
+
   // Diffuse term
-  f32 l_dot_n = dot_v3(norm, g_directional_light.direction);
+  f32 l_dot_n = dot_v3(norm, light_dir);
   if (l_dot_n <= 0.0f) {
     goto RETURN_OUTPUT_COLOUR;
   }
@@ -127,7 +146,7 @@ internal FragmentResult phong_shader_fragment(void *shader,
 
   // Specular term
   V3f _2_l_dot_n_norm = num_mul_v3(norm, 2.0f * l_dot_n);
-  V3f reflected = sub_v3(_2_l_dot_n_norm, g_directional_light.direction);
+  V3f reflected = sub_v3(_2_l_dot_n_norm, light_dir);
   f32 r_dot_v = dot_v3(reflected, data->position);
   if (r_dot_v <= 0.0f) {
     goto RETURN_OUTPUT_COLOUR;