Alexei Soupikov

Highly Parallel Fast KD-tree Construction for Interactive Ray Tracing of Dynamic Scenes

We present a highly parallel, linearly scalable technique of kd‐tree construction for ray tracing of dynamic geometry. We use conventional kd‐tree compatible with the high performing algorithms such as MLRTA or frustum tracing. Proposed technique offers exceptional construction speed maintaining reasonable kd‐tree quality for rendering stage. The algorithm builds a kd‐tree from scratch each frame, thus prior knowledge of motion /deformation or motion constraints are not required. We achieve nearly real‐time performance of 7‐12 FPS for models with 200K of dynamic triangles at 1024x1024 resolution with shadows and textures.

Improving Kd-tree quality at a reasonable construction cost

We consider construction of high-quality kd-tree and investigate the effect of techniques based on perfect splits. The main idea of perfect splits is clipping of objects straddling the splitting planes during the construction. This effectively results in reducing the number of references in leaves while also generating new potential split positions. We derive an efficient algorithm for triangle clipping/assignment and show how to avoid problems for parallel construction using clipping. Investigating the influence of using clipping results at different kd-tree construction stages, we finally come up with on-the-fly pruning algorithm that improves rendering performance by up to 25% decreasing construction time as well.

Consistent normal interpolation

Rendering a polygonal surface with Phong normal interpolation allows shading to appear as it would for a true curved surface while maintaining the efficiency and simplicity of coarse polygonal geometry. However, this approximation fails in certain situations, especially for grazing viewing directions. Well-known problems include physically impossible reflections and implausible illumination. Some of these artifacts can be mitigated through special-case processing, although no universal or generally accepted approaches are available. In particular, all known solutions that guarantee that reflected rays will always point outward from the surface also create discontinuities in the reflection ray direction. We present a simple modification of Phong normal interpolation that allows physically plausible reflections and creates an appearance of a smooth surface. We introduce an additional scalar parameter that characterizes the deviation between per-vertex normals and per face normals and use it to adjust linearly interpolated normals. The proposed technique eliminates perceptually objectionable artifacts caused by inconsistencies between the shading and geometric normals while retaining most of the practical advantages and simplicity of the original Phong formulation.

Efficient post-processing antialiasing on integrated GPUs

Most modern games use deferred shading, in which shading is performed only for visible pixels, allowing greater artistic freedom in scene composing and lighting. However, traditional antialiasing techniques, such as super-sampling and multi-sampling, are not well-suited for deferred shading pipeline, since all subsamples have to be explicitly written to output buffer.