fixed bug in shapes/Plane which would return negative results, fixed bug in main/Scene which would not check for shape to be non-null after calling getRayClosestHit()

git-svn-id: svn://anubis/fart/trunk@161 7f9b0f55-74a9-4bce-be96-3c2cd072584d

shapes/Plane.cc

@@ -38,8 +38,11 @@ Shape::IntersectionList Plane::intersect(refptr<Shape> _this, const Ray & ray)
     Solver::Result solutions = solver.solve();
     if (solutions.numResults > 0)
     {
-        Vector isect_point = ray_inv[solutions.results[0]];
-        res.add(Intersection(_this, m_transform.transform_point(isect_point)));
+        if (solutions.results[0] > 0.0)
+        {
+            Vector isect_point = ray_inv[solutions.results[0]];
+            res.add(Intersection(_this, m_transform.transform_point(isect_point)));
+        }
     }
     return res;
 }