From a1fae1a38fc3cdb82e379a069fce886cb3fa88ae Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Wed, 13 Jan 2010 16:21:28 -0500
Subject: Clean up internal raytracing API a bit.

---
 libdimension/color.c           |  6 ++++++
 libdimension/dimension/color.h |  5 +++++
 libdimension/raytrace.c        | 22 +++++++++-------------
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/libdimension/color.c b/libdimension/color.c
index 8201a8f..5220dfa 100644
--- a/libdimension/color.c
+++ b/libdimension/color.c
@@ -84,6 +84,12 @@ const dmnsn_color dmnsn_cyan = {
   .trans  = 0.0
 };
 
+bool
+dmnsn_color_is_black(dmnsn_color color)
+{
+  return color.R == 0.0 && color.G == 0.0 && color.B == 0.0;
+}
+
 /* sRGB's `C' function */
 static double dmnsn_sRGB_C(double Clinear) {
   /*
diff --git a/libdimension/dimension/color.h b/libdimension/dimension/color.h
index 67fa032..43edbff 100644
--- a/libdimension/dimension/color.h
+++ b/libdimension/dimension/color.h
@@ -25,6 +25,8 @@
 #ifndef DIMENSION_COLOR_H
 #define DIMENSION_COLOR_H
 
+#include <stdbool.h>
+
 /* Internally, we use sRGB color. */
 typedef struct {
   double filter, trans; /* Filter transparancy only lets light of this color
@@ -67,6 +69,9 @@ extern const dmnsn_color dmnsn_black, dmnsn_white, dmnsn_red, dmnsn_green,
 /* Standard whitepoint, determined by the conversion of sRGB white to CIE XYZ */
 extern const dmnsn_CIE_XYZ dmnsn_whitepoint;
 
+/* Is this color black? */
+bool dmnsn_color_is_black(dmnsn_color color);
+
 /* Color conversions */
 
 dmnsn_color dmnsn_color_from_XYZ(dmnsn_CIE_XYZ XYZ);
diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
index 0165870..bb44587 100644
--- a/libdimension/raytrace.c
+++ b/libdimension/raytrace.c
@@ -20,7 +20,6 @@
 
 #include "dimension_impl.h"
 #include <unistd.h> /* For sysconf */
-#include <stdbool.h>
 
 /*
  * Boilerplate for multithreading
@@ -337,12 +336,10 @@ dmnsn_raytrace_pigment(const dmnsn_raytrace_state *state)
 }
 
 /* Get the color of a light ray at an intersection point */
-static bool
+static dmnsn_color
 dmnsn_raytrace_light_ray(const dmnsn_raytrace_state *state,
-                         const dmnsn_light *light, dmnsn_color *color)
+                         const dmnsn_light *light)
 {
-  *color = dmnsn_black;
-
   dmnsn_vector x0 = dmnsn_line_point(state->intersection->ray,
                                      state->intersection->t);
   dmnsn_line shadow_ray = dmnsn_new_line(x0, dmnsn_vector_sub(light->x0, x0));
@@ -351,9 +348,9 @@ dmnsn_raytrace_light_ray(const dmnsn_raytrace_state *state,
 
   /* Search for an object in the way of the light source */
   if (dmnsn_vector_dot(shadow_ray.n, state->intersection->normal) < 0.0)
-    return false;
+    return dmnsn_black;
 
-  *color = (*light->light_fn)(light, x0);
+  dmnsn_color color = (*light->light_fn)(light, x0);
 
   unsigned int level = state->level;
   while (level) {
@@ -373,21 +370,20 @@ dmnsn_raytrace_light_ray(const dmnsn_raytrace_state *state,
 
     dmnsn_color pigment = dmnsn_raytrace_pigment(&shadow_state);
     if (pigment.filter || pigment.trans) {
-      *color = dmnsn_color_filter(*color, pigment);
+      color = dmnsn_color_filter(color, pigment);
       shadow_ray.x0 = dmnsn_line_point(shadow_ray, shadow_caster->t);
       shadow_ray.n  = dmnsn_vector_sub(light->x0, shadow_ray.x0);
       shadow_ray = dmnsn_line_add_epsilon(shadow_ray);
     } else {
-      *color = dmnsn_black;
       dmnsn_delete_intersection(shadow_caster);
-      return false;
+      return dmnsn_black;
     }
 
     dmnsn_delete_intersection(shadow_caster);
     --level;
   }
 
-  return true;
+  return color;
 }
 
 static dmnsn_color
@@ -410,8 +406,8 @@ dmnsn_raytrace_lighting(const dmnsn_raytrace_state *state)
   for (i = 0; i < dmnsn_array_size(state->scene->lights); ++i) {
     dmnsn_array_get(state->scene->lights, i, &light);
 
-    dmnsn_color light_color;
-    if (dmnsn_raytrace_light_ray(state, light, &light_color)) {
+    dmnsn_color light_color = dmnsn_raytrace_light_ray(state, light);
+    if (!dmnsn_color_is_black(light_color)) {
       if (state->scene->quality & DMNSN_RENDER_FINISH
           && finish && (finish->diffuse_fn || finish->specular_fn))
       {
-- 
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