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Frustum-traced raster shadows: revisiting irregular z-buffers

Published:27 February 2015Publication History

ABSTRACT

We present a real-time system that renders antialiased hard shadows using irregular z-buffers (IZBs). For subpixel accuracy, we use 32 samples per pixel at roughly twice the cost of a single sample. Our system remains interactive on a variety of game assets and CAD models while running at 1080p and 2160p and imposes no constraints on light, camera or geometry, allowing fully dynamic scenes without precomputation. Unlike shadow maps we introduce no spatial or temporal aliasing, smoothly animating even subpixel shadows from grass or wires.

Prior irregular z-buffer work relies heavily on GPU compute. Instead we leverage the graphics pipeline, including hardware conservative raster and early-z culling. We observe a duality between irregular z-buffer performance and shadow map quality; this allows common shadow map algorithms to reduce our cost. Compared to state-of-the-art ray tracers, we spawn similar numbers of triangle intersections per pixel yet completely rebuild our data structure in under 2 ms per frame.

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    • Published in

      cover image ACM Conferences
      i3D '15: Proceedings of the 19th Symposium on Interactive 3D Graphics and Games
      February 2015
      133 pages
      ISBN:9781450333924
      DOI:10.1145/2699276

      Copyright © 2015 ACM

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      Publication History

      • Published: 27 February 2015

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