There are three paradoxal objects which are exposed on a marble table in a museum. These impossible objects show how interesting it can be to by-pass physical laws of the reality within raytraced images.

Penrose' three beams : there are three perpendicular beams which finally join each other. One beam is on the z axis, another on the x axis, and the third on the y axis. It is impossible for these three beams to make a cycle : that is the optical illusion.

Dirk Huizer' cube : the point situated in the middle of the object is simultaneously the center of the cube and the corner of it. Here is the impossibility.

Mitsumasa Anno' construction set : each of three beam has one extremity which is stretched in a vertical way and its other in the horizontal way, that's why it is impossible to realize such an object.

Two different technical tricks were used here. The 'construction set' was created simply with a rotation of one plane of a beam in order to seem like if it wasn't rotated. The 'Dirk Huizer cube' and the 'Penrose's three beams' were created with elements which are situated in front of others, but which are cut in order to fit exactly the backward elements so that it seem they are simultaneously in the front and in the back of the scene. The projection used to render the scene is not the normal 3D projection, it is an isometric projection which is obtained simply by setting big values to the coordinates of the camera's location and direction so that the camera is very far from the scene without seeing nothing cause of the reduction of size. This makes rays become parallel so that the projection become isometric. That allows tricks to be easier to render without seeing them.