Interactive Indirect Illumination Using Voxel Cone Tracing

Abstract

Indirect illumination is an important element for realistic image synthesis, but its computation is expensive and highly dependent on the complexity of the scene and of the BRDF of the involved surfaces. While off-line computation and pre-baking can be acceptable for some cases, many applications (games, simulators, etc.) require real-time or interactive approaches to evaluate indirect illumination. We present a novel algorithm to compute indirect lighting in real-time that avoids costly precomputation steps and is not restricted to low-frequency illumination. It is based on a hierarchical voxel octree representation generated and updated on the fly from a regular scene mesh coupled with an approximate voxel cone tracing that allows for a fast estimation of the visibility and incoming energy. Our approach can manage two light bounces for both Lambertian and glossy materials at interactive framerates (25-70FPS). It exhibits an almost scene-independent performance and can handle complex scenes with dynamic content thanks to an interactive octree-voxelization scheme. In addition, we demonstrate that our voxel cone tracing can be used to efficiently estimate Ambient Occlusion.

A Topological Approach to Voxelization

“…A simple analysis also reveals that the GPU‐based voxelization method used by Forest et al [FBP09] and Crassin et al [CNS*11] is 6‐separating. They do three passes over the input, and in each pass rasterize the primitives along three axis‐aligned projections.…”

“…Voxelization with a single 2D projection . An interesting corollary follows from the thinness property and the equivalence of the 3‐axis rasterization [FBP09, CNS*11] with the crosshairs target. When a planar triangle is projected along the dominant axis of its geometric normal vector, every pixel whose center lies in the projected triangle produces a unique voxel in the corresponding voxel column.…”

A Voxel-Based Rendering Pipeline for Large 3D Line Sets

“…All these approaches subdivide the model into a sparse volume, storing only small volume "bricks" along the initial model surface, and use a compute-based octree traversal to render the contained surface. The potential of voxelbased rendering approaches to efficiently simulate global illumination effects has been demonstrated, for instance, in [5], [31]. The survey by Joenssen et al [32] provides a general overview of approaches for simulating global illumination effects on volumetric data sets.…”

“…For a selected quantization resolution, the minimum number of bytes that is required to encode this information is used. Overall, our approach requires 4, 5, and 6 bytes per line, respectively, when quantization resolutions of (4,8), (16,32) and (64,128) are used. Table 1 compares the memory consumption for different resolution and quantization levels with the memory that is required to store the original lines on the GPU, using 32 bit float values per vertex component and 1 byte per vertex to map to transparency or color.…”

Procedural feature generation for volumetric terrains using voxel grammars

“…SVOs are used by [13] to create a fast approximation to global illumination in real time scenes by constructing a two-part octree consisting of a node pool and a brick pool. The node pool linearly stores the structure of the octree in contiguous memory in order to maximize cache coherency when querying the data structure.…”