From 5eab850f84d30bfe2042b439c65b7e83db581348 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Mon, 9 Nov 2009 14:07:14 -0500
Subject: Rudimentary light/shadow handling.

---
 libdimension/raytrace.c | 66 ++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 57 insertions(+), 9 deletions(-)

(limited to 'libdimension/raytrace.c')

diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index 6cb6d8b..da78411 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -259,11 +259,7 @@ static dmnsn_color
 dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
                      dmnsn_kD_splay_tree *kD_splay_tree, dmnsn_color color)
 {
-  dmnsn_intersection *intersection;
-  const dmnsn_texture *texture;
-  const dmnsn_pigment *pigment;
-
-  intersection = dmnsn_kD_splay_search(kD_splay_tree, ray);
+  dmnsn_intersection *intersection = dmnsn_kD_splay_search(kD_splay_tree, ray);
 
   if (intersection) {
     /* Default to black if we have no texture/pigment */
@@ -271,13 +267,15 @@ dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
 
     if (scene->quality >= DMNSN_RENDER_PIGMENT) {
       /* Use the default texture if given a NULL texture */
-      texture = intersection->texture ? intersection->texture
-                                      : scene->default_texture;
+      const dmnsn_texture *texture
+        = intersection->texture ? intersection->texture
+                                : scene->default_texture;
 
       if (texture) {
         /* Use the default pigment if given a NULL pigment */
-        pigment = texture->pigment ? texture->pigment
-                                   : scene->default_texture->pigment;
+        const dmnsn_pigment *pigment
+          = texture->pigment ? texture->pigment
+                             : scene->default_texture->pigment;
 
         if (pigment) {
           color = (*pigment->pigment_fn)(
@@ -288,6 +286,56 @@ dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
       }
     }
 
+    if (scene->quality >= DMNSN_RENDER_LIGHTS) {
+      dmnsn_color illum = dmnsn_color_mul(0.3, color);
+
+      const dmnsn_light *light;
+      unsigned int i;
+
+      for (i = 0; i < dmnsn_array_size(scene->lights); ++i) {
+        dmnsn_array_get(scene->lights, i, &light);
+        dmnsn_vector x0 = dmnsn_line_point(ray, intersection->t);
+        dmnsn_line shadow_ray = dmnsn_line_construct(
+          dmnsn_vector_add(
+            x0,
+            dmnsn_vector_mul(1.0e-6, dmnsn_vector_sub(light->x0, x0))
+          ),
+          dmnsn_vector_sub(light->x0, x0)
+        );
+
+        dmnsn_intersection *shadow_caster
+          = dmnsn_kD_splay_search(kD_splay_tree, shadow_ray);
+
+        if (!shadow_caster || shadow_caster->t > 1.0) {
+          dmnsn_vector object_normal = x0;
+          dmnsn_vector normal = dmnsn_vector_normalize(
+            dmnsn_vector_add(
+              dmnsn_vector_normalize(dmnsn_vector_sub(ray.x0, x0)),
+              dmnsn_vector_normalize(dmnsn_vector_sub(light->x0, x0))
+            )
+          );
+
+          illum = dmnsn_color_add(
+            dmnsn_color_mul(
+              dmnsn_vector_dot(normal, object_normal),
+              dmnsn_color_illuminate((*light->light_fn)(light, x0), color)
+            ),
+            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);
+        color = illum;
+      }
+    }
+
     /* Delete the intersection */
     dmnsn_delete_intersection(intersection);
   }
-- 
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