reworked Scene::traceRayRecurse() to handle backfaces properly for refraction

git-svn-id: svn://anubis/fart/trunk@378 7f9b0f55-74a9-4bce-be96-3c2cd072584d

main/Scene.cc

@@ -119,8 +119,7 @@ void Scene::renderPixel(int x, int y, unsigned char * pixel)
 
 Color Scene::traceRay(const Ray & ray)
 {
-    static refptr<Material> air = new Material();
+    return traceRayRecurse(ray, m_max_depth, 1.0, NULL);
-    return traceRayRecurse(ray, m_max_depth, 1.0, air);
 }
 
 /**
@@ -129,7 +128,11 @@ Color Scene::traceRay(const Ray & ray)
 Color Scene::traceRayRecurse(const Ray & ray, int depth, double factor,
         refptr<Material> last_material)
 {
-    Color color;
+    static refptr<Material> air = new Material();
+    Color color(0, 0, 0);
+
+    if (last_material.isNull())
+        last_material = air;
 
     Shape::Intersection hit = getRayClosestHit(ray);
 
@@ -139,12 +142,10 @@ Color Scene::traceRayRecurse(const Ray & ray, int depth, double factor,
         refptr<Material> material = hit.shape->getMaterial();
 
         /* check for backfaces */
-        if (ray.getDirection() % hit.normal > 0.0)
+        bool frontface = ray.getDirection() % hit.normal < 0.0;
-        {
-            /* if dot product is positive, this is a back-face */
-            hit.normal = -hit.normal;
-        }
 
+        if (frontface)
+        {
             color = computePhong(material,
                                  ray,
                                  hit.position,
@@ -187,6 +188,19 @@ Color Scene::traceRayRecurse(const Ray & ray, int depth, double factor,
                 }
             }
         }
+        else
+        {
+            material = air;
+            Vector jitter_surface_point = hit.position
+                                          + ray.getDirection() * 0.0001;
+            Vector refracted_direction =
+                ray.getDirection().refract(-hit.normal,
+                        last_material->getRefraction(),
+                        material->getRefraction());
+            Ray newRay(jitter_surface_point, refracted_direction);
+            color = traceRayRecurse(newRay, depth, factor, material);
+        }
+    }
 
     return color;
 }

scenes/for-test.fart

@@ -3,7 +3,7 @@ scene
 {
     camera
     {
-        position <0, 0, 40>
+        position <0, -40, 40>
         look_at <0, 100, 5>
     }
 
@@ -17,6 +17,12 @@ scene
         color <0, 0.8, 1>
     }
 
+    define material glass
+    {
+        transparency 1
+        refraction 1.5
+    }
+
     plane
     {
         position <0, 0, 1>, 0
@@ -34,8 +40,16 @@ scene
             {
                 radius 10
                 translate <$x, $y, 10>
+                if ($x == 0 && $y == 0)
+                {
+                    material glass
+                    translate <0, 0, 20>
+                }
+                else
+                {
                     material mat
                 }
             }
         }
     }
+}