Shape is now an abstract class and can't be instanciated.

Change derived shape to only deal with local calculation they don't need anymore to deal with how they've been transformed.

source/shapes/shape.cpp

@@ -22,12 +22,21 @@ Shape::Shape(ShapeType type)
 
 Intersect Shape::intersect(Ray r)
 {
-    return Intersect();
+    return this->localIntersect(this->invTransform(r));
 };
 
 Tuple Shape::normalAt(Tuple point)
 {
-    return Vector(0, 0, 0);
+    Tuple local_point = this->inverseTransform * point;
+
+    Tuple local_normal = this->localNormalAt(local_point);
+
+    Tuple world_normal = this->inverseTransform.transpose() * local_normal;
+
+    /* W may get wrong, so hack it. This is perfectly normal as we are using a 4x4 matrix instead of a 3x3 */
+    world_normal.w = 0;
+
+    return world_normal.normalise();
 }
 
 void Shape::setTransform(Matrix transform)