Splat-based ray tracing of point clouds

Abstract

Point-based surface representations have gained increasing interest in the computer graphics community within the last decade. Surface splatting established as one of the main rendering techniques for point clouds. We present a ray-tracing approach for objects whose surfaces are represented by point clouds. Our approach is based on casting rays and intersecting them with splats. Since ray-tracing methods require smoothly changing surface normals for producing the desired photorealistic results, splat generation must include the derivation of such normals. We determine a neighborhood around each point of the point cloud, estimate the surface normal at each of the points, compute splats with varying radii that cover the surface, and use the normals of all points that are covered by each splat to generate a smoothly varying normal field for each splat. This part of the computation is view-independent and, thus, can be precomputed. During the rendering step, ray-splat intersections are performed, where the normal at the intersection point is interpolated using local coordinates of the splat’s normal field. Care has to be taken where splats overlap. We speed up the computations of the ray-splat intersections using an octree data structure.