Change directional light to point light

src/model/obj.h

@@ -33,11 +33,11 @@ struct phong_material {
   f32 shininess;
 };
 
-typedef struct directional_light DirectionalLight;
-struct directional_light {
+typedef struct point_light PointLight;
+struct point_light {
   V3f diffuse_intensity;
   V3f specular_intensity;
-  V3f direction;
+  V3f position;
 };
 
 typedef struct model Model;