Blister: GPU-based rendering of Boolean combinations of free-form triangulated shapes

Abstract

By combining depth peeling with a linear formulation of a Boolean expression called Blist, the Blister algorithm renders an arbitrary CSG model of n primitives in at most k steps, where k is the number of depth-layers in the arrangement of the primitives. Each step starts by rendering each primitive to produce candidate surfels on the next depth-layer. Then, it renders the primitives again, one at a time, to classify the candidate surfels against the primitive and to evaluate the Boolean expression directly on the GPU. Since Blist does not expand the CSG expression into a disjunctive (sum-of-products) form, Blister has O(kn) time complexity. We explain the Blist formulation while providing algorithms for CSG-to-Blist conversion and Blist-based parallel surfel classification. We report real-time performance for nontrivial CSG models. On hardware with an 8-bit stencil buffer, we can render all possible CSG expressions with 3909 primitives.