Single Distance Clipping in Vertex Shader for VR Portal

VR portal is a powerful tool connecting multiple VR spaces and providing impressive visual effects. The implementation of VR portals requires the VR compositor to perform a clipping operation. For performance reason, the clipping needs to be performed in vertex shader, which prevents most of existing algorithm to be used here. This paper proposes a novel algorithm that performs the clipping operation with a single distance value. The proposed algorithm is well suited for the vertex shader, and can handle both normal clipping and inverse clipping. This enables users to view a VR portal from both sides. The proposed algorithm also saves the number of clip planes for other purposes, and its performance is superior to the traditional algorithm with multiple clip planes.