Shader-based tessellation to save memory bandwidth in a mobile multimedia processor

Abstract

in this paper, we propose an architecture of tessellation hardware to save memory bandwidth in a mobile multimedia processor. To reduce the implementation overhead, floating-point computations of tessellation are accelerated by the conventional CPU pipeline, and only tessellation-specific control logic is handled by an additional hardware unit. Tightly coupled with a vertex shader, the additional unit dynamically produces topological configurations and parametric coordinates of refinement patterns in the type of indexed triangle strips for object-level adaptive tessellation. The topological configurations improve the efficiency of the vertex cache so as to avoid redundant shader operations. Since the proposed tessellator is area-efficient and does not require intermediate memory accesses, its architecture is especially appropriate for the mobile environment, which adopts a shared bus and unified external memory architecture. The proposed tessellator is fabricated on a chip using 0.18 mu m CMOS technology. With 6.2% additional hardware for a dual-core vertex shader, the implemented chip performs 120 Mvertices/s vertex shading and saves memory bandwidth up to 250 times in tessellation. (C) 2009 Elsevier Ltd. All rights reserved.