Make finish callback a propper BRDF.

5 files changed, 53 insertions, 31 deletions

diff --git a/libdimension/dimension/geometry.h b/libdimension/dimension/geometry.h
index 86a0111..08ac1b3 100644
--- a/libdimension/dimension/geometry.h
+++ b/libdimension/dimension/geometry.h
@@ -77,6 +77,14 @@ dmnsn_line_construct(dmnsn_vector x0, dmnsn_vector n)
 /* Vector and matrix arithmetic */
 
 DMNSN_INLINE dmnsn_vector
+dmnsn_vector_negate(dmnsn_vector rhs)
+{
+  /* 3 negations */
+  dmnsn_vector v = { -rhs.x, -rhs.y, -rhs.z };
+  return v;
+}
+
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_add(dmnsn_vector lhs, dmnsn_vector rhs)
 {
   /* 3 additions */
diff --git a/libdimension/dimension/texture.h b/libdimension/dimension/texture.h
index 4d0e2d7..e5a1bfd 100644
--- a/libdimension/dimension/texture.h
+++ b/libdimension/dimension/texture.h
@@ -58,12 +58,15 @@ typedef struct dmnsn_finish dmnsn_finish;
 
 /* Finish callback */
 typedef dmnsn_color dmnsn_finish_fn(const dmnsn_finish *finish,
-                                    dmnsn_color color, dmnsn_vector x0,
-                                    dmnsn_vector normal,
-                                    dmnsn_vector reflected);
+                                    dmnsn_color light, dmnsn_color color,
+                                    dmnsn_vector ray, dmnsn_vector normal,
+                                    dmnsn_vector viewer);
 
 /* dmnsn_finish definition */
 struct dmnsn_finish {
+  /* Ambient contribution factor */
+  double ambient;
+
   /* Callbacks */
   dmnsn_finish_fn *finish_fn;
   dmnsn_free_fn *free_fn;
diff --git a/libdimension/finishes.c b/libdimension/finishes.c
index befe6c6..d70cfb7 100644
--- a/libdimension/finishes.c
+++ b/libdimension/finishes.c
@@ -21,12 +21,15 @@
 #include "dimension.h"
 #include <stdlib.h> /* For malloc */
 
-static dmnsn_color
+dmnsn_color
 dmnsn_diffuse_finish_fn(const dmnsn_finish *finish,
-                         dmnsn_color color, dmnsn_vector x0,
-                         dmnsn_vector normal, dmnsn_vector reflected)
+                        dmnsn_color light, dmnsn_color color,
+                        dmnsn_vector ray, dmnsn_vector normal,
+                        dmnsn_vector viewer)
 {
-  return dmnsn_color_mul(dmnsn_vector_dot(normal, reflected), color);
+  double diffuse = dmnsn_vector_dot(ray, normal);
+  dmnsn_color illum = dmnsn_color_illuminate(light, color);
+  return dmnsn_color_mul(diffuse, illum);
 }
 
 /* A diffuse finish */
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index 3a266a2..7608d85 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -20,6 +20,7 @@
 
 #include "dimension_impl.h"
 #include <unistd.h> /* For sysconf */
+#include <stdbool.h>
 
 /* Payload type for passing arguments to worker thread */
 
@@ -279,8 +280,8 @@ dmnsn_raytrace_pigment(dmnsn_intersection *intersection, dmnsn_scene *scene)
 }
 
 static dmnsn_color
-dmnsn_raytrace_shadow(dmnsn_intersection *intersection, dmnsn_scene *scene,
-                      dmnsn_kD_splay_tree *kD_splay_tree, dmnsn_color color)
+dmnsn_raytrace_lighting(dmnsn_intersection *intersection, dmnsn_scene *scene,
+                        dmnsn_kD_splay_tree *kD_splay_tree, dmnsn_color color)
 {
   /* Use the default texture if given a NULL texture */
   const dmnsn_texture *texture = intersection->texture ? intersection->texture
@@ -292,13 +293,17 @@ dmnsn_raytrace_shadow(dmnsn_intersection *intersection, dmnsn_scene *scene,
     finish = texture->finish ? texture->finish : scene->default_texture->finish;
   }
 
-  dmnsn_color illum = dmnsn_color_mul(0.1, color);
+  /* The illuminated color */
+  dmnsn_color illum = dmnsn_black;
+  if (finish)
+    illum = dmnsn_color_mul(finish->ambient, 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(intersection->ray, intersection->t);
     dmnsn_line shadow_ray = dmnsn_line_construct(
       /* Add epsilon*(light->x0 - x0) to avoid hitting ourself with the shadow
@@ -310,31 +315,30 @@ dmnsn_raytrace_shadow(dmnsn_intersection *intersection, dmnsn_scene *scene,
       dmnsn_vector_sub(light->x0, x0)
     );
 
+    /* Search for an object in the way of the light source */
     dmnsn_intersection *shadow_caster
       = dmnsn_kD_splay_search(kD_splay_tree, shadow_ray);
+    bool lit = !shadow_caster || shadow_caster->t > 1.0;
+    dmnsn_delete_intersection(shadow_caster);
 
-    if (!shadow_caster || shadow_caster->t > 1.0) {
-      dmnsn_vector normal = intersection->normal;
-      dmnsn_vector reflected = dmnsn_vector_normalize(
-        dmnsn_vector_add(
-          dmnsn_vector_normalize(dmnsn_vector_sub(intersection->ray.x0, x0)),
-          dmnsn_vector_normalize(dmnsn_vector_sub(light->x0, x0))
-        )
-      );
-
-      dmnsn_color effective
-        = dmnsn_color_illuminate((*light->light_fn)(light, x0), color);
+    if (scene->quality >= DMNSN_RENDER_FINISH && finish) {
+      dmnsn_color light_color = dmnsn_black;
+      if (lit)
+        light_color = (*light->light_fn)(light, x0);
 
-      if (scene->quality >= DMNSN_RENDER_FINISH && finish) {
-        illum = dmnsn_color_add((*finish->finish_fn)(finish, effective, x0,
-                                                     normal, reflected),
-                                illum);
-      } else {
-        illum = effective;
-      }
+      dmnsn_vector ray    = dmnsn_vector_normalize(shadow_ray.n);
+      dmnsn_vector normal = intersection->normal;
+      dmnsn_vector viewer
+        = dmnsn_vector_normalize(dmnsn_vector_negate(intersection->ray.n));
+
+      /* Get this light's color contribution to the object */
+      dmnsn_color contrib = (*finish->finish_fn)(finish,
+                                                 light_color, color,
+                                                 ray, normal, viewer);
+      illum = dmnsn_color_add(contrib, illum);
+    } else if (lit) {
+      illum = color;
     }
-
-    dmnsn_delete_intersection(shadow_caster);
   }
 
   return illum;
@@ -356,7 +360,10 @@ dmnsn_raytrace_shoot(dmnsn_line ray, dmnsn_scene *scene,
     }
 
     if (scene->quality >= DMNSN_RENDER_LIGHTS) {
-      color = dmnsn_raytrace_shadow(intersection, scene, kD_splay_tree, color);
+      color = dmnsn_raytrace_lighting(intersection,
+                                      scene,
+                                      kD_splay_tree,
+                                      color);
     }
 
     dmnsn_delete_intersection(intersection);
diff --git a/tests/libdimension/tests.c b/tests/libdimension/tests.c
index 85c43a6..fe914f4 100644
--- a/tests/libdimension/tests.c
+++ b/tests/libdimension/tests.c
@@ -32,6 +32,7 @@ dmnsn_new_default_scene()
 
   /* Default finish */
   scene->default_texture->finish = dmnsn_new_diffuse_finish();
+  scene->default_texture->finish->ambient = 0.1;
 
   /* Background color */
   dmnsn_sRGB sRGB = { .R = 0.0, .G = 0.0, .B = 0.1 };