Real-Time Soft Shadow by A-Buffer.

We present a new real-time soft shadow algorithm by A-Buffer in virtual environment. The key idea is to use A-Buffer to store the whole scene information and then to accurately compute soft shadow. In the first pass, the scenes are drawn in the center view of the complex area lights, and the target fragments of per pixel are stored into an A-Buffer. The second is to calculate the occlusion percentage according to the cone which is consisted of the shaded point and area lights from the view of the camera. The occlusion percentage is the ration of blocked area and sampled area within the cone, and it is used to calculate the shadow factor. Our algorithm could produce more realistic shadow effects in real-time and adapt to the complex scenes.