added scenes/trans-boxes.fart, changed Scene to consider all back-faces as front-faces by inverting the normal vector, fixed bug in Scene::calculateLightContribution() which was messing up shadow values and back-face intensities for transparent objects

git-svn-id: svn://anubis/fart/trunk@187 7f9b0f55-74a9-4bce-be96-3c2cd072584d

main/Scene.cc

@@ -158,6 +158,13 @@ Color Scene::traceRayRecurse(const Ray & ray, int depth, double factor)
         Vector surfacePoint = ray[hit.dist];
         Vector surfaceNormal = hit.shape->getNormalAt(surfacePoint);
 
+        /* check for backfaces */
+        if (ray.getDirection() % surfaceNormal > 0.0)
+        {
+            /* if dot product is positive, this is a back-face */
+            surfaceNormal = -surfaceNormal;
+        }
+
         color = computePhong(material,
                              ray,
                              surfacePoint,
@@ -215,7 +222,6 @@ Scene::ShapeDistance Scene::getRayClosestHit(const Ray & ray)
         {
             refptr<Shape> shape = intersections[i].shape;
             const Vector & isect_point = intersections[i].vector;
-            Vector normal = shape->getNormalAt(isect_point);
             double intersect_dist = (isect_point - ray.getOrigin()).mag();
             if (foundOne == false || intersect_dist < hit.dist)
             {
@@ -313,7 +319,9 @@ double Scene::calculateLightContribution(const Ray & toLight,
         if ( contrib < SCENE_FACTOR_THRESHOLD )
             break;
 
-        dist_so_far += hit.dist + 0.0001;
+        double offset = hit.dist + 0.0001;
+        dist_so_far += offset;
+        currentRay = currentRay.shift(offset);
     }
 
     return contrib;