Math: handle exceptions on 0 values + simplification.

Signed-off-by: Nicolas Adenis-Lamarre <nicolas.adenis.lamarre@gmail.com>
Rendering : ugly mode

Merging moto rendering of ghost/rider.
Rendering from anchors, not from positions.

Signed-off-by: Nicolas Adenis-Lamarre <nicolas.adenis.lamarre@gmail.com>