Let’s Have a Min/Max Party

December 11, 2008 at 5:54 am (News, Papers)

Today I was waiting for a session to begin at SIGGRAPH ASIA and began to think about how there are several cool papers that exploit min/max  images. A min/max image is an image pyramid that is sort of like a quadtree. The bottom level of the hierarchy is the original image while the elements in each subsequent level of the hierarchy contain the minimum and maximum of four elements in the previous level. So it’s sort of like a mip map, but instead of averaging values, you store the min and max of the previous level. This min/max hierarchy can be generated quickly in log n passes but can be used for making conservative estimations for large regions of your image. Refer to the following papers:

Maximum Mipmaps for Fast, Accurate, and Scalable Dynamic Height Field Rendering by A. Tevs, I. Ihrke, H.-P. Seidel

– Uses min/max maps to ray trace height fields. I feel like this idea has been around for ages but here it is all packaged up with a neat little bow.

Fast GPU Ray Tracing of Dynamic Meshes using Geometry Images by Nathan Carr, Jared Hoberock, Keenan Crane, John C. Hart.

– Uses min/max hierarchies of Geometry Images to accelerate the ray tracing of meshes.

Real-time Soft Shadow Mapping by Backprojection by Gaël Guennebaud, Loïc Barthe, Mathias Paulin
High-Quality Adaptive Soft Shadow Mapping by Gaël Guennebaud, Loïc Barthe, Mathias Paulin

–  I’ve ranted about these papers before. These works generate min/max hierarchies of shadow camera depth images to perform efficient blocker searches for soft shadow rendering, and also to determine penumbra regions for further optimization.

March of the Froblins SIGGRAPH course notes by Jeremy Shopf, Joshua Barczak, Christopher Oat, Natalya Tatarchuk

– Used a min/max hierarchy of the depth buffer to occlusion cull agents in our crowd simulation. Technically this only used the max portion of the hierarchy, but I didn’t want to title this Let’s have a Min/Max Party (Min is Optional).

Anyway, I think it’s kind of neat. I’m going to make another post tomorrow night about an awesome paper that’s here at the conference but I don’t want to write about it until I have a chance to clear up some nebulous parts of the paper with the author.

In other news, I received official word that the GDC lecture I proposed was accepted so I guess I will be seeing some of you in San Francisco next year in March. I’m excited about this talk because it came directly out of a post on this blog. Turns out this isn’t a waste of time after all!

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2 Comments

  1. Robert 'Groby' Blum said,

    For some strange reasons, min/max maps feel strangely similar to wavelet compressed maps. Am I completely off my rocker, or is this indeed true?

  2. levelofdetail said,

    They’re similar in that they are essentially trees and each internal node contains information that can be used in place of children.

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