In the game there is a directional light for simulating sun light, this is also the light casting the shadows on ground. It happens that when the car runs onto shaded ground, its own shadow become invisible, so, the car seems unattached from the floor.
For this reason we needed to add a sort of ambient occlusion under the car’s body.
A first attempt was by using a second directional light set perfectly perpendicular to the ground. This trick was working on most situation but gave strange artifacts under trees foliage, arcs, bridges and when the car was jumping. Other negative side effect was the computation cost of such solution.
For the above reasons we switched to blob shadow for faking AO under the car. We made a first try by using light projector but it was an unlucky try: light projector is broken or it expects some kind of image we are not aware of. At the end we back to the old glorious mapped poligon. A first intersect_ray, cast fom the center of the car, returns a point used for set the position where to place the plane under the car, then, a second intersect_ray, casted a bit ahead, returns a second point for aligning the blob with the ground. the code used for the positioning/aligning of the the shadow looks like this:
blob.look_at_from_pos(point1.position, point2.position, point1.normal)