From 6d7f2ba7016e35e998290ce0eade8c2517922fab Mon Sep 17 00:00:00 2001
From: Eric-Paul Ickhorn <ericp.ickhorn@gmail.com>
Date: Sun, 17 Dec 2023 12:12:41 +0100
Subject: [PATCH] Fixed projection matrix and made translation column-major

---
 core/src-c/matrix.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/core/src-c/matrix.c b/core/src-c/matrix.c
index f7f036b..d99e171 100644
--- a/core/src-c/matrix.c
+++ b/core/src-c/matrix.c
@@ -109,9 +109,9 @@ rr_vec4f_s rr_mat4f_multiply_vec4f(rr_mat4f_s matrix, rr_vec4f_s vector)
 
 void rr_mat4f_translate(rr_mat4f_s *matrix, rr_vec3f_s xyz)
 {
-    matrix->values[0][3] = xyz.x;
-    matrix->values[1][3] = xyz.y;
-    matrix->values[2][3] = xyz.z;
+    matrix->values[3][0] = xyz.x;
+    matrix->values[3][1] = xyz.y;
+    matrix->values[3][2] = xyz.z;
 }
 
 rr_mat4f_s rr_mat4f_rotate_x(float radians)
@@ -166,31 +166,29 @@ rr_mat4f_s rr_mat4f_rotate_xyz(float x_rad, float y_rad, float z_rad)
 
 rr_mat4f_s rr_mat4f_perspective(float fov, float near_plane, float far_plane, float aspect_ratio)
 {
-    float plane_range = far_plane - near_plane;
-    float scale_x     = (2 * near_plane) / (plane_range * aspect_ratio * 2);
-    float scale_y     = near_plane / plane_range;
-    float scale_z     = -(far_plane + near_plane) / (far_plane - near_plane);
-    float pos_z       = tanf(fov / 2) * near_plane;
+    float a             = tanf(fov / 2.0f) * near_plane;
+    float planes_sum    = far_plane + near_plane;
+    float planes_range  = far_plane - near_plane;
 
     rr_mat4f_s matrix;
-    matrix.values[0][0] = scale_x;
+    matrix.values[0][0] = 1 / aspect_ratio;
     matrix.values[0][1] = 0.0f;
     matrix.values[0][2] = 0.0f;
     matrix.values[0][3] = 0.0f;
 
     matrix.values[1][0] = 0.0f;
-    matrix.values[1][1] = scale_y;
+    matrix.values[1][1] = aspect_ratio;
     matrix.values[1][2] = 0.0f;
     matrix.values[1][3] = 0.0f;
 
     matrix.values[2][0] = 0.0f;
     matrix.values[2][1] = 0.0f;
-    matrix.values[2][2] = scale_z;
+    matrix.values[2][2] = -(planes_sum / planes_range);
     matrix.values[2][3] = -1.0f;
 
     matrix.values[3][0] = 0.0f;
     matrix.values[3][1] = 0.0f;
-    matrix.values[3][2] = pos_z;
+    matrix.values[3][2] = -(2 * planes_sum / planes_range);
     matrix.values[3][3] = 0.0f;
 
     return matrix;