From 324de43f622ace14a51384cdf8bb7bb190b58699 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Tue, 17 Nov 2009 19:08:00 -0500
Subject: Implement phong shading.

---
 libdimension/finishes.c | 51 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 10 deletions(-)

(limited to 'libdimension/finishes.c')

diff --git a/libdimension/finishes.c b/libdimension/finishes.c
index d70cfb7..a7cfaea 100644
--- a/libdimension/finishes.c
+++ b/libdimension/finishes.c
@@ -20,25 +20,56 @@
 
 #include "dimension.h"
 #include <stdlib.h> /* For malloc */
+#include <math.h>
 
 dmnsn_color
-dmnsn_diffuse_finish_fn(const dmnsn_finish *finish,
-                        dmnsn_color light, dmnsn_color color,
-                        dmnsn_vector ray, dmnsn_vector normal,
-                        dmnsn_vector viewer)
+dmnsn_phong_finish_fn(const dmnsn_finish *finish,
+                      dmnsn_color light, dmnsn_color color,
+                      dmnsn_vector ray, dmnsn_vector normal,
+                      dmnsn_vector viewer)
 {
-  double diffuse = dmnsn_vector_dot(ray, normal);
-  dmnsn_color illum = dmnsn_color_illuminate(light, color);
-  return dmnsn_color_mul(diffuse, illum);
+  double *params = finish->ptr;
+
+  double diffuse  = params[0];
+  double specular = params[1];
+  double exp      = params[2];
+
+  /* Diffuse component */
+  double diffuse_factor = diffuse*dmnsn_vector_dot(ray, normal);
+  dmnsn_color diffuse_color
+    = dmnsn_color_mul(diffuse_factor, dmnsn_color_illuminate(light, color));
+
+  /* Specular component */
+
+  dmnsn_vector proj = dmnsn_vector_mul(2*dmnsn_vector_dot(ray, normal), normal);
+  dmnsn_vector reflected = dmnsn_vector_sub(proj, ray);
+
+  double specular_factor
+    = specular*pow(dmnsn_vector_dot(reflected, viewer), exp);
+  dmnsn_color specular_color = dmnsn_color_mul(specular_factor, light);
+
+  return dmnsn_color_add(diffuse_color, specular_color);
 }
 
-/* A diffuse finish */
+/* A phong finish */
 dmnsn_finish *
-dmnsn_new_diffuse_finish()
+dmnsn_new_phong_finish(double diffuse, double specular, double exp)
 {
   dmnsn_finish *finish = dmnsn_new_finish();
   if (finish) {
-    finish->finish_fn = &dmnsn_diffuse_finish_fn;
+    double *params = malloc(3*sizeof(double));
+    if (!params) {
+      dmnsn_delete_finish(finish);
+      return NULL;
+    }
+
+    params[0] = diffuse;
+    params[1] = specular;
+    params[2] = exp;
+
+    finish->ptr       = params;
+    finish->finish_fn = &dmnsn_phong_finish_fn;
+    finish->free_fn   = &free;
   }
   return finish;
 }
-- 
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