Fix barycentric coordinates calculation (#2)

Reviewed-on: #2

	* Set up for debugging
	* Replace get_barycentric_coords with different calculation
	* Update commented lines
	* Add V3_ELEM_COUNT macro
	* Change loop in barycentric coordinates calculation function
	* Update debug values
	* Simplify barycentric coordinates function
	* Remove debug lines
Co-authored-by: Abdelrahman <said.abdelrahman89@gmail.com>
Co-committed-by: Abdelrahman <said.abdelrahman89@gmail.com>

src/main.c

@@ -41,8 +41,8 @@ int main(void) {
   PhongMaterial material = {
       .ambient = 0.3f,
       .diffuse = 1.5f,
-      .specular = 0.5f,
-      .shininess = 0.1f,
+      .specular = 2.0f,
+      .shininess = 1.5f,
   };
   obj.material = material;
 

src/model/render.c

@@ -25,9 +25,7 @@ internal void fill_triangle(Render *render, ShaderID shader,
                             const Model *model, RenderType type);
 internal TriangleBBox get_triangle_bbox(const Image *img,
                                         V3f vertices[TRIANGLE_VERTICES]);
-internal V3f get_barycentric_coords(f32 d00, f32 d01, f32 d11, f32 denom,
-                                    const V2f *v0, const V2f *v1,
-                                    const V2f *v2);
+internal V3f get_barycentric_coords(V3f a, V3f b, V3f c, V3f p);
 internal V3f get_viewport_vertex(const V3f *vertex, const Image *img);
 
 bool init_render(Arena *arena, Render *render, u64 width, u64 height) {
@@ -109,14 +107,8 @@ internal void fill_triangle(Render *render, ShaderID shader,
   V3f vert0 = vertices[0];
   V3f vert1 = vertices[1];
   V3f vert2 = vertices[2];
+  V3f point;
 
-  V2f v0 = V2(V2f, f32, vert0.x, vert0.y, vert1.x, vert1.y);
-  V2f v1 = V2(V2f, f32, vert0.x, vert0.y, vert2.x, vert2.y);
-  f32 d00 = dot_v2(v0, v0);
-  f32 d01 = dot_v2(v0, v1);
-  f32 d11 = dot_v2(v1, v1);
-  f32 denom = d00 * d11 - d01 * d01;
-  V2f v2;
   V3f coords;
   f32 z;
   f32 zbuf;
@@ -134,9 +126,9 @@ internal void fill_triangle(Render *render, ShaderID shader,
 
   for (u64 y = bbox.y0; y <= bbox.y1; ++y) {
     for (u64 x = bbox.x0; x <= bbox.x1; ++x) {
-      v2 = V2(V2f, f32, vert0.x, vert0.y, x, y);
-      coords = get_barycentric_coords(d00, d01, d11, denom, &v0, &v1, &v2);
-      if (coords.x < 0.0f || coords.y < 0.0f || coords.x + coords.y > 1.0f) {
+      point = (V3f){x, y, 1.0f};
+      coords = get_barycentric_coords(vert0, vert1, vert2, point);
+      if (coords.x < 0.0f || coords.y < 0.0f || coords.z < 0.0f) {
         continue;
       }
 
@@ -200,21 +192,16 @@ internal TriangleBBox get_triangle_bbox(const Image *img,
   };
 }
 
-internal V3f get_barycentric_coords(f32 d00, f32 d01, f32 d11, f32 denom,
-                                    const V2f *v0, const V2f *v1,
-                                    const V2f *v2) {
-  if (denom == 0.0f) {
-    return (V3f){-INFINITY, -INFINITY, -INFINITY};
+internal V3f get_barycentric_coords(V3f a, V3f b, V3f c, V3f p) {
+  V3f x_vec = V3(V3f, f32, c.x, b.x, a.x, a.x, a.x, p.x);
+  V3f y_vec = V3(V3f, f32, c.y, b.y, a.y, a.y, a.y, p.y);
+
+  V3f u = cross_product(x_vec, y_vec);
+  if (fabsf(u.z) < 1e-2) {
+    return (V3f){-1.0f, 1.0f, 1.0f};
   }
 
-  f32 d20 = dot_v2((*v2), (*v0));
-  f32 d21 = dot_v2((*v2), (*v1));
-
-  f32 v = (d11 * d20 - d01 * d21) / denom;
-  f32 w = (d00 * d21 - d01 * d20) / denom;
-  f32 u = 1.0f - v - w;
-
-  return (V3f){v, w, u};
+  return (V3f){1.0f - (u.x + u.y) / u.z, u.y / u.z, u.x / u.z};
 }
 
 internal V3f get_viewport_vertex(const V3f *vertex, const Image *img) {

src/vec/vec.h

@@ -5,6 +5,8 @@
 #include "typed_list.h"
 #include <math.h>
 
+#define V3_ELEM_COUNT 3
+
 typedef struct i64x2 V2i;
 struct i64x2 {
   i64 x;
@@ -32,16 +34,21 @@ struct f32x2 {
 typedef struct f32x3 V3f;
 struct f32x3 {
   union {
-    f32 x;
-    f32 r;
-  };
-  union {
-    f32 y;
-    f32 g;
-  };
-  union {
-    f32 z;
-    f32 b;
+    f32 elements[V3_ELEM_COUNT];
+    struct {
+      union {
+        f32 x;
+        f32 r;
+      };
+      union {
+        f32 y;
+        f32 g;
+      };
+      union {
+        f32 z;
+        f32 b;
+      };
+    };
   };
 };