An interleaved Parallel Volume Renderer with PC-clusters Antonio Garcia and Han-Wei Shen Dept of Computer Science Ohio State University Eurographics Workshop on Parallel Viz 2002

Parallel volume rendering Image-space partitioning – advantages –Load balancing –Low communication overhead –Access to full volume (data redistribution overhead if not stored locally) Object-space partitioning –Storage scalability (with no of processors) –Image compositing overhead Hybrid method

Object Space + Image Space Divide procs into groups Renders a portion of the volume Every member interleaves data samples of the volume and pixels on the screen. So, distribute data according to pixel and volume

Offline Setup p p Display = p 2 Volume = s 3 No of procs = N M (# procs in a group) s s s s s s G (# of groups) G = N/M I = interleaving factor; M = 2 i

Interleaving factor When i=0, Sort-last –N groups have partition of volume, When i is max = log(n) –1 group with N members –Sort-first G (# of groups) = N M (#procs in a group) = 2 0 = 1 S 3 /N G (# of groups) = 1 M (#procs in a group) = 2 logn = N S3S3 S3S3 S3S3 S3S3

Group Each processor has - S 3 /N 4 processors

Online – Rendering ++ Same local id Binary-swap image composition

Results -Load imbalance – Assymetrical data -Image quality Conclusions Low interleaving factor - low composition cost