Calculate surface normals in intersection callbacks.

4 files changed, 23 insertions, 11 deletions

diff --git a/libdimension/dimension/object.h b/libdimension/dimension/object.h
index 0f53406..0393d94 100644
--- a/libdimension/dimension/object.h
+++ b/libdimension/dimension/object.h
@@ -31,6 +31,9 @@ typedef struct {
   dmnsn_line ray;
   double t;
 
+  /* The surface normal at the intersection point */
+  dmnsn_vector normal;
+
   /* The texture at the intersection point */
   const dmnsn_texture *texture;
 } dmnsn_intersection;
diff --git a/libdimension/kD_splay_tree.c b/libdimension/kD_splay_tree.c
index 5c6289d..77e57dd 100644
--- a/libdimension/kD_splay_tree.c
+++ b/libdimension/kD_splay_tree.c
@@ -304,10 +304,12 @@ dmnsn_kD_splay_search_recursive(dmnsn_kD_splay_node *node, dmnsn_line ray,
 dmnsn_intersection *
 dmnsn_kD_splay_search(dmnsn_kD_splay_tree *tree, dmnsn_line ray)
 {
-  dmnsn_kD_splay_search_result result;
-  result = dmnsn_kD_splay_search_recursive(tree->root, ray, -1.0);
+  dmnsn_kD_splay_search_result result
+    = dmnsn_kD_splay_search_recursive(tree->root, ray, -1.0);
+
   if (result.node)
     dmnsn_kD_splay(tree, result.node);
+
   return result.intersection;
 }
 
@@ -353,6 +355,12 @@ dmnsn_kD_splay_search_recursive(dmnsn_kD_splay_node *node, dmnsn_line ray,
         result.node = node;
         result.intersection = result_temp.intersection;
         t = result.intersection->t;
+
+        /* Transform the normal vector back to the observer's view */
+        result.intersection->normal = dmnsn_matrix_vector_mul(
+          node->object->trans,
+          result.intersection->normal
+        );
       } else {
         dmnsn_delete_intersection(result_temp.intersection);
       }
diff --git a/libdimension/objects.c b/libdimension/objects.c
index 721d04d..b5e4a32 100644
--- a/libdimension/objects.c
+++ b/libdimension/objects.c
@@ -71,6 +71,7 @@ dmnsn_sphere_intersection_fn(const dmnsn_object *sphere, dmnsn_line line)
       intersection = dmnsn_new_intersection();
       intersection->ray     = line;
       intersection->t       = t;
+      intersection->normal  = dmnsn_line_point(line, t);
       intersection->texture = sphere->texture;
     }
   }
@@ -114,7 +115,7 @@ static dmnsn_intersection *
 dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
 {
   double t = -1.0, t_temp;
-  dmnsn_vector p;
+  dmnsn_vector p, normal;
   dmnsn_intersection *intersection = NULL;
 
   /* Six ray-plane intersection tests (x, y, z) = +/- 1.0 */
@@ -127,6 +128,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
+      normal = dmnsn_vector_construct(-1.0, 0.0, 0.0);
     }
 
     /* x = 1.0 */
@@ -136,6 +138,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
+      normal = dmnsn_vector_construct(1.0, 0.0, 0.0);
     }
   }
 
@@ -147,6 +150,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
+      normal = dmnsn_vector_construct(0.0, -1.0, 0.0);
     }
 
     /* y = 1.0 */
@@ -156,6 +160,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
+      normal = dmnsn_vector_construct(0.0, 1.0, 0.0);
     }
   }
 
@@ -167,6 +172,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
+      normal = dmnsn_vector_construct(0.0, 0.0, -1.0);
     }
 
     /* z = 1.0 */
@@ -176,6 +182,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
         && t_temp >= 0.0 && (t < 0.0 || t_temp < t))
     {
       t = t_temp;
+      normal = dmnsn_vector_construct(0.0, 0.0, 1.0);
     }
   }
 
@@ -183,6 +190,7 @@ dmnsn_cube_intersection_fn(const dmnsn_object *cube, dmnsn_line line)
     intersection = dmnsn_new_intersection();
     intersection->ray     = line;
     intersection->t       = t;
+    intersection->normal  = normal;
     intersection->texture = cube->texture;
   }
 
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index dc017f5..262929f 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -307,7 +307,7 @@ dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
           = dmnsn_kD_splay_search(kD_splay_tree, shadow_ray);
 
         if (!shadow_caster || shadow_caster->t > 1.0) {
-          dmnsn_vector object_normal = x0;
+          dmnsn_vector object_normal = intersection->normal;
           dmnsn_vector normal = dmnsn_vector_normalize(
             dmnsn_vector_add(
               dmnsn_vector_normalize(dmnsn_vector_sub(ray.x0, x0)),
@@ -322,13 +322,6 @@ dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
             ),
             illum
           );
-          illum = dmnsn_color_add(
-            dmnsn_color_mul(
-              0.1*dmnsn_vector_dot(normal, object_normal),
-              dmnsn_color_illuminate((*light->light_fn)(light, x0), dmnsn_white)
-            ),
-            illum
-          );
         }
 
         dmnsn_delete_intersection(shadow_caster);