Synchronized-tracing of implicit surfaces

TL;DR

This paper introduces a tile-based rendering pipeline for implicit surfaces that enables efficient, synchronized ray tracing of complex blobtree models without preprocessing, using a novel A-buffer and sparse traversal techniques.

Contribution

It presents a new rendering pipeline that handles dynamic primitive updates efficiently and scales to thousands of primitives using a synchronized, thread-coherent approach.

Findings

Pipeline scales well to thousands of primitives

No preprocessing needed for primitive updates

Achieves coherent field evaluation within workgroups

Abstract

Implicit surfaces are known for their ability to represent smooth objects of arbitrary topology thanks to hierarchical combinations of primitives using a structure called a blobtree. We present a new tile-based rendering pipeline well suited for modeling scenarios, i.e., no preprocessing is required when primitive parameters are updated. When using approximate signed distance fields, we rely on compact, smooth CSG operators - extended from standard bounded operators - to compute a tight volume of interest for all primitives of the blobtree. The pipeline relies on a low-resolution A-buffer storing the primitives of interest of a given screen tile. The A-buffer is then used during ray processing to synchronize threads within a subfrustum. This allows coherent field evaluation within workgroups. We use a sparse bottom-up tree traversal to prune the blobtree on-the-fly which allows us to decorrelate field evaluation complexity from the full blobtree size. The ray processing itself is done using the sphere-tracing algorithm. The pipeline scales well to surfaces consisting of thousands of primitives.