Curved Ray-Casting for Displacement Mapping in the GPU

摘要

To achieve interactive speed, displacement mapping in the GPU is typically implemented in two steps: vertex shading/rasterization of the base surface and pixel shading. Pixel shading applies the height map relative to the image plane of the base surface, casts view rays to the height field through each pixel, finds the intersection point with the height field, and computes the color of that point. Here, the ray-casting process involves significant errors; The spatial relationship between the ray and the base surface is not preserved between the ray and the image plane of the base surface. The errors result in incorrect silhouettes. To address this problem, we curve the ray so that the spatial relationship between the (linear) ray and the base surface is preserved between the curved ray and the image plane of the base surface. This method reduces intersection errors, producing more satisfactory silhouettes, self-occlusions and shadows.