added getNormalAt() to Shape & Sphere, trying to get basic lighting

git-svn-id: svn://anubis/fart/trunk@44 7f9b0f55-74a9-4bce-be96-3c2cd072584d

shapes/Shape.h

@@ -4,6 +4,7 @@
 
 #include "util/Solver.h"
 #include "util/Ray.h"
+#include "util/Vector.h"
 #include "util/Transform.h"
 
 class Shape
@@ -12,6 +13,7 @@ class Shape
         virtual Solver::Result intersect(const Ray & ray) = 0;
         void setTransform(const Transform & t) { m_transform = t; }
         Transform & getTransform() { return m_transform; }
+        virtual Vector getNormalAt(const Vector & pt) = 0;
 
     protected:
         Transform m_transform;

shapes/Sphere.cc

@@ -34,3 +34,9 @@ Solver::Result Sphere::intersect(const Ray & ray)
     }
     return res;
 }
+
+Vector Sphere::getNormalAt(const Vector & pt)
+{
+    Vector normal = pt;
+    return normal.normalize();
+}

shapes/Sphere.h

@@ -9,6 +9,7 @@ class Sphere : public Shape
     public:
         Sphere(double radius);
         Solver::Result intersect(const Ray & ray);
+        Vector getNormalAt(const Vector & pt);
 
     private:
         double m_radius;