SSAO 1.5.1

Screen space ambient occlusion (SSAO) is implemented, use

python ./render.py --scene lambo --name lambo-back.xml --iter_num 8000 --arch cuda --type ao

to find out. The following images are rendered using RTX3060-laptop with a interactive preview, without it, the rendering speed is 81 fps and 161 fps, respectively. The scene consists of 300k primitives.

Lambo scene (67 fps)	Lambo-back scene (120 fps)

Note that the first image has some weird patches, which might be caused by erroneous normal vector and is not the problem of this renderer.