From dc09a4508529c2616e85b675b0e76f525aafe28b Mon Sep 17 00:00:00 2001
From: Abdelrahman <said.abdelrahman89@gmail.com>
Date: Sun, 28 Jul 2024 23:09:16 +0100
Subject: [PATCH] Fix filling triangles

---
 src/main.c |  2 +-
 src/obj.c  | 21 +++++++++++++--------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/src/main.c b/src/main.c
index 6a965aa..eed15f7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -28,7 +28,7 @@ int main(void) {
     return TINY_EXIT_IMAGE_INIT_FAILED;
   }
 
-  Model model = load_obj_file(arena, "resources/triangle.obj");
+  Model model = load_obj_file(arena, "resources/head.obj");
   if (IS_NULL_MODEL(model)) {
     return TINY_EXIT_MODEL_LOAD_FAILED;
   }
diff --git a/src/obj.c b/src/obj.c
index 594e3a8..cf96ce3 100644
--- a/src/obj.c
+++ b/src/obj.c
@@ -7,6 +7,11 @@
 #include <stdio.h>
 
 #define TRIANGLE_VERTICES 3
+#define dot_v2(V1, V2) ((f32)V1.x * (f32)V2.x + (f32)V1.y * (f32)V2.y)
+#define dot_v3(V1, V2)                                                         \
+  ((f32)V1.x * (f32)V2.x + (f32)V1.y * (f32)V2.y + (f32)V1.z * (f32)V2.z)
+#define V2(T, ELEM_T, X0, Y0, X1, Y1)                                          \
+  ((T){(ELEM_T)X1 - (ELEM_T)X0, (ELEM_T)Y1 - (ELEM_T)Y0})
 
 typedef struct triangle_bbox TriangleBBox;
 struct triangle_bbox {
@@ -149,18 +154,18 @@ internal void fill_triangle(Image *img, Vertex vertices[TRIANGLE_VERTICES],
   get_image_coordinates(&(vertices[1]), img, &v1x, &v1y);
   get_image_coordinates(&(vertices[2]), img, &v2x, &v2y);
 
-  V2i ab = {.x = (i64)v1x - (i64)v0x, .y = (i64)v1y - (i64)v0y};
-  V2i ac = {.x = (i64)v2x - (i64)v0x, .y = (i64)v2y - (i64)v0y};
-  f32 d00 = (f32)ab.x * (f32)ab.x + (f32)ab.y + (f32)ab.y;
-  f32 d01 = (f32)ab.x * (f32)ac.x + (f32)ab.y + (f32)ac.y;
-  f32 d11 = (f32)ac.x * (f32)ac.x + (f32)ac.y + (f32)ac.y;
+  V2i ab = V2(V2i, i64, v0x, v0y, v1x, v1y);
+  V2i ac = V2(V2i, i64, v0x, v0y, v2x, v2y);
+  f32 d00 = dot_v2(ab, ab);
+  f32 d01 = dot_v2(ab, ac);
+  f32 d11 = dot_v2(ac, ac);
   f32 denom = (f32)d00 * (f32)d11 - (f32)d01 * (f32)d01;
   V2i ap;
   V3f coords;
 
   for (u64 y = bbox.y0; y < bbox.y1; ++y) {
     for (u64 x = bbox.x0; x < bbox.x1; ++x) {
-      ap = (V2i){.x = (i64)x - (i64)v0x, .y = (i64)y - (i64)v0y};
+      ap = V2(V2i, i64, v0x, v0y, x, y);
       coords = get_barycentric_coords(d00, d01, d11, denom, &ab, &ac, &ap);
       if (coords.x < 0.0f || coords.y < 0.0f || coords.z < 0.0f) {
         continue;
@@ -190,8 +195,8 @@ internal TriangleBBox get_triangle_bbox(const Image *img,
 internal V3f get_barycentric_coords(f32 d00, f32 d01, f32 d11, f32 denom,
                                     const V2i *ab, const V2i *ac,
                                     const V2i *ap) {
-  f32 d20 = (f32)ap->x * (f32)ab->x + (f32)ap->y + (f32)ab->y;
-  f32 d21 = (f32)ap->x * (f32)ac->x + (f32)ap->y + (f32)ac->y;
+  f32 d20 = dot_v2((*ap), (*ab));
+  f32 d21 = dot_v2((*ap), (*ac));
 
   f32 v = (d11 * d20 - d01 * d21) / denom;
   f32 w = (d00 * d21 - d01 * d20) / denom;