From 40b180db2833e4e6ef835a463ca15ff865ce0d18 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Thu, 25 Feb 2010 22:03:11 -0500
Subject: Point the normal vectors away from the object.

---
 libdimension/cube.c       | 12 ++++++------
 libdimension/diffuse.c    |  2 +-
 libdimension/raytrace.c   |  3 ++-
 libdimension/reflective.c |  2 +-
 libdimension/sphere.c     |  4 ----
 5 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/libdimension/cube.c b/libdimension/cube.c
index 9815eb6..9588f24 100644
--- a/libdimension/cube.c
+++ b/libdimension/cube.c
@@ -64,7 +64,7 @@ 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_new_vector(-copysign(1.0, line.n.x), 0.0, 0.0);
+      normal = dmnsn_new_vector(-1.0, 0.0, 0.0);
     }
 
     /* x = 1.0 */
@@ -74,7 +74,7 @@ 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_new_vector(-copysign(1.0, line.n.x), 0.0, 0.0);
+      normal = dmnsn_new_vector(1.0, 0.0, 0.0);
     }
   }
 
@@ -86,7 +86,7 @@ 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_new_vector(0.0, -copysign(1.0, line.n.y), 0.0);
+      normal = dmnsn_new_vector(0.0, -1.0, 0.0);
     }
 
     /* y = 1.0 */
@@ -96,7 +96,7 @@ 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_new_vector(0.0, -copysign(1.0, line.n.y), 0.0);
+      normal = dmnsn_new_vector(0.0, 1.0, 0.0);
     }
   }
 
@@ -108,7 +108,7 @@ 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_new_vector(0.0, 0.0, -copysign(1.0, line.n.z));
+      normal = dmnsn_new_vector(0.0, 0.0, -1.0);
     }
 
     /* z = 1.0 */
@@ -118,7 +118,7 @@ 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_new_vector(0.0, 0.0, -copysign(1.0, line.n.z));
+      normal = dmnsn_new_vector(0.0, 0.0, 1.0);
     }
   }
 
diff --git a/libdimension/diffuse.c b/libdimension/diffuse.c
index 75d4c52..910e23f 100644
--- a/libdimension/diffuse.c
+++ b/libdimension/diffuse.c
@@ -32,7 +32,7 @@ dmnsn_diffuse_finish_fn(const dmnsn_finish *finish,
                         dmnsn_vector ray, dmnsn_vector normal)
 {
   double *diffuse = finish->ptr;
-  double diffuse_factor = (*diffuse)*dmnsn_vector_dot(ray, normal);
+  double diffuse_factor = fabs((*diffuse)*dmnsn_vector_dot(ray, normal));
   dmnsn_color ret
     = dmnsn_color_mul(diffuse_factor, dmnsn_color_illuminate(light, color));
   ret.filter = 0.0;
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index 3fa873c..826cc58 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -323,7 +323,8 @@ dmnsn_raytrace_light_ray(const dmnsn_raytrace_state *state,
   shadow_ray = dmnsn_line_add_epsilon(shadow_ray);
 
   /* Check if we're casting a shadow on ourself */
-  if (dmnsn_vector_dot(shadow_ray.n, state->intersection->normal) < 0.0)
+  if (dmnsn_vector_dot(shadow_ray.n, state->intersection->normal)
+      * dmnsn_vector_dot(state->viewer, state->intersection->normal) < 0.0)
     return dmnsn_black;
 
   dmnsn_color color = (*light->light_fn)(light, state->r);
diff --git a/libdimension/reflective.c b/libdimension/reflective.c
index 9667072..726bf8d 100644
--- a/libdimension/reflective.c
+++ b/libdimension/reflective.c
@@ -37,7 +37,7 @@ dmnsn_reflective_finish_fn(const dmnsn_finish *finish,
                            dmnsn_vector ray, dmnsn_vector normal)
 {
   dmnsn_reflection_params *params = finish->ptr;
-  double reflection = pow(dmnsn_vector_dot(ray, normal), params->falloff);
+  double reflection = pow(fabs(dmnsn_vector_dot(ray, normal)), params->falloff);
 
   return dmnsn_color_illuminate(
     dmnsn_color_gradient(params->min, params->max, reflection),
diff --git a/libdimension/sphere.c b/libdimension/sphere.c
index d994248..f30c964 100644
--- a/libdimension/sphere.c
+++ b/libdimension/sphere.c
@@ -74,10 +74,6 @@ dmnsn_sphere_intersection_fn(const dmnsn_object *sphere, dmnsn_line line)
       intersection->normal   = dmnsn_line_point(line, t);
       intersection->texture  = sphere->texture;
       intersection->interior = sphere->interior;
-
-      /* Flip the normal if we're inside the sphere */
-      if (dmnsn_vector_dot(line.n, intersection->normal) > 0.0)
-        intersection->normal = dmnsn_vector_negate(intersection->normal);
     }
   }
 
-- 
cgit v1.2.3