From 185f44252f729f741f2e454ce6e0f3d88419fe50 Mon Sep 17 00:00:00 2001
From: Abdelrahman <said.abdelrahman89@gmail.com>
Date: Sun, 25 Aug 2024 01:32:54 +0100
Subject: [PATCH] Flip the Y texture coordinate when loading the OBJ model

---
 src/model/obj.c      | 2 +-
 src/shader/shaders.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/model/obj.c b/src/model/obj.c
index ed153ed..b1f3aa8 100644
--- a/src/model/obj.c
+++ b/src/model/obj.c
@@ -56,7 +56,7 @@ Model load_obj_file(Arena *arena, const char *filename, const char *texture,
     } else if (strncmp(identifier, "vt", 8) == 0) {
       sscanf(line + 2, "%f %f", &u, &v);
       coord.u = u;
-      coord.v = v;
+      coord.v = 1.0f - v;
       list_append(V2f, arena, model.texture_coordinates, coord);
     } else if (strncmp(identifier, "f", 8) == 0) {
       sscanf(line + 2, "%lu/%lu/%lu %lu/%lu/%lu %lu/%lu/%lu", &fp0, &tx0, &vn0,
diff --git a/src/shader/shaders.c b/src/shader/shaders.c
index 2a2bfb9..4f8cc0f 100644
--- a/src/shader/shaders.c
+++ b/src/shader/shaders.c
@@ -94,7 +94,7 @@ internal FragmentResult phong_shader_fragment(void *shader,
   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;
+    u64 nm_y = data->tex_coords.v * model->normal->height;
 
     Colour pixel = get_pixel(Colour, model->normal, nm_x, nm_y);
     hnorm = (V4f){
@@ -118,7 +118,7 @@ internal FragmentResult phong_shader_fragment(void *shader,
   Colour output;
   if (model->texture) {
     u64 tx_x = data->tex_coords.u * model->texture->width;
-    u64 tx_y = (1.0f - data->tex_coords.v) * model->texture->height;
+    u64 tx_y = data->tex_coords.v * model->texture->height;
     output = get_pixel(Colour, model->texture, tx_x, tx_y);
   } else {
     output = *colour;