From b0cebb67f8ce211143d4fa040fde33c7a0eaf5a5 Mon Sep 17 00:00:00 2001
From: Abdelrahman <said.abdelrahman89@gmail.com>
Date: Sat, 14 Sep 2024 18:33:04 +0100
Subject: [PATCH] Store inverted final matrix in the shader

---
 src/shader/shader_base.inc |  1 +
 src/shader/shaders.c       | 34 ++++++++++++++++++++--------------
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/src/shader/shader_base.inc b/src/shader/shader_base.inc
index 5fb7dc7..77a0e90 100644
--- a/src/shader/shader_base.inc
+++ b/src/shader/shader_base.inc
@@ -4,4 +4,5 @@ M4x4f proj_mv;
 M4x4f proj_mv_inv_t;
 M4x4f viewport;
 M4x4f final;
+M4x4f final_inv;
 VertexData vertices[TRIANGLE_VERTICES];
diff --git a/src/shader/shaders.c b/src/shader/shaders.c
index f2d13f7..104ded2 100644
--- a/src/shader/shaders.c
+++ b/src/shader/shaders.c
@@ -6,15 +6,15 @@
 #include "shader.h"
 #include "vec.h"
 
+ShaderID depth                = {0};
 ShaderID perspective_diffuse  = {0};
 ShaderID perspective_albedo   = {0};
 ShaderID orthographic_diffuse = {0};
 ShaderID orthographic_albedo  = {0};
-ShaderID depth                = {0};
 
+internal DepthShader depth_shader = {0};
 internal Shader      perspective  = {0};
 internal Shader      orthographic = {0};
-internal DepthShader depth_shader = {0};
 
 internal V3f g_ambient_light = {0.1f, 0.1f, 0.1f};
 internal V3f g_eye           = {0.2f, -0.1f, 0.5f};
@@ -25,6 +25,19 @@ internal V3f g_light_dir     = {1.0f, -1.0f, 1.0f};
 internal M4x4f get_projection_matrix(ProjectionType projection_type);
 
 void load_shaders(M4x4f vp) {
+  // Set up depth shader matrices
+  M4x4f depth_model_view = lookat(g_light_dir, g_target, g_up);
+  M4x4f depth_projection = projection(0.0f);
+
+  // Set up depth shader
+  depth_shader.proj_mv       = mat4x4_mul(depth_projection, depth_model_view);
+  depth_shader.proj_mv_inv_t = mat4x4_inv(mat4x4_transpose(depth_shader.proj_mv));
+  depth_shader.viewport      = vp;
+  depth_shader.final         = mat4x4_mul(depth_shader.viewport, depth_shader.proj_mv);
+  depth_shader.light_dir     = mat3x3_mul_vec3(depth_shader.proj_mv, g_light_dir);
+  normalise_v3(depth_shader.light_dir);
+
+  // Set up main shaders matrices
   M4x4f model_view              = lookat(g_eye, g_target, g_up);
   M4x4f orthographic_projection = get_projection_matrix(PROJECTION_TYPE_ORTHOGRAPHIC);
   M4x4f perspective_projection  = get_projection_matrix(PROJECTION_TYPE_PERSPECTIVE);
@@ -34,6 +47,8 @@ void load_shaders(M4x4f vp) {
   perspective.proj_mv_inv_t = mat4x4_inv(mat4x4_transpose(perspective.proj_mv));
   perspective.viewport      = vp;
   perspective.final         = mat4x4_mul(perspective.viewport, perspective.proj_mv);
+  perspective.final_inv     = mat4x4_inv(perspective.final);
+  perspective.shadow_matrix = mat4x4_mul(depth_shader.final, perspective.final_inv);
   perspective.light_dir     = mat3x3_mul_vec3(perspective.proj_mv, g_light_dir);
   normalise_v3(perspective.light_dir);
   perspective.ambient       = g_ambient_light;
@@ -43,27 +58,18 @@ void load_shaders(M4x4f vp) {
   orthographic.proj_mv_inv_t = mat4x4_inv(mat4x4_transpose(orthographic.proj_mv));
   orthographic.viewport      = vp;
   orthographic.final         = mat4x4_mul(orthographic.viewport, orthographic.proj_mv);
+  orthographic.final_inv     = mat4x4_inv(perspective.final);
+  orthographic.shadow_matrix = mat4x4_mul(depth_shader.final, orthographic.final_inv);
   orthographic.light_dir     = mat3x3_mul_vec3(orthographic.proj_mv, g_light_dir);
   normalise_v3(orthographic.light_dir);
   orthographic.ambient       = g_ambient_light;
 
-  // Set up depth shader
-  M4x4f depth_model_view = lookat(g_light_dir, g_target, g_up);
-  M4x4f depth_projection = projection(0.0f);
-
-  depth_shader.proj_mv       = mat4x4_mul(depth_projection, depth_model_view);
-  depth_shader.proj_mv_inv_t = mat4x4_inv(mat4x4_transpose(depth_shader.proj_mv));
-  depth_shader.viewport      = vp;
-  depth_shader.final         = mat4x4_mul(depth_shader.viewport, depth_shader.proj_mv);
-  depth_shader.light_dir     = mat3x3_mul_vec3(depth_shader.proj_mv, g_light_dir);
-  normalise_v3(depth_shader.light_dir);
-
   // Register shaders
+  depth                = register_shader(&depth_shader, depth_shader_vertex, depth_shader_fragment);
   perspective_diffuse  = register_shader(&perspective, general_shader_vertex, diffuse_shader_fragment);
   perspective_albedo   = register_shader(&perspective, general_shader_vertex, albedo_shader_fragment);
   orthographic_diffuse = register_shader(&orthographic, general_shader_vertex, diffuse_shader_fragment);
   orthographic_albedo  = register_shader(&orthographic, general_shader_vertex, albedo_shader_fragment);
-  depth                = register_shader(&depth_shader, depth_shader_vertex, depth_shader_fragment);
 }
 
 internal M4x4f get_projection_matrix(ProjectionType projection_type) {