Fast Normal Map Generation for Simplified Meshes

Abstract

Approximating detailed models with coarse, normal mapped meshes is a very efficient method for real-time rendering of complex objects with fine surface detail. In this paper, we present a new and fast normal map construction algorithm. We scan-convert each triangle of the simplified model, which results in a regularly spaced point set on the surface of each triangle. The original model and all these point samples of the simplified model are rendered from uniformly distributed camera positions. The actual normal map is created by computing the corresponding normals for the point sets. For each point, the normal of the closest point from the high resolution mesh over the set of all camera positions is chosen. Our approach works for general triangle meshes and exploits fully common graphics rendering hardware. Normal map construction times are generally in the range of only a few seconds even for large models. We render our normal-mapped meshes in real-time with a slightly modified version of the standard bump-mapping algorithm. In order to evaluate the approximation error, we investigate the distance and normal errors for normal-mapped meshes. Our investigation of the approximation errors shows that using more than 12 viewpoints does not result in a further improvement in the normal maps for our test cases.