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Submitted by , posted on 10 August 2002
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Image Description, by
Here's a pair of screenshots from my Chunked LOD terrain demo. My
goal was to create a hardware-friendly LOD method without too many
compromises. It turned out pretty well. The system has high triangle
throughput at high framerates, low CPU overhead, works within a
guaranteed max pixel error, and has full geomorphing (no pops). The
number of triangles rendered is higher than with a primitive-level LOD
scheme like Lindstrom-Koller or ROAM, by 1.5-2x or so, but the CPU
overhead is much lower. The view above is scaled down from a pair of
1024x768 screenshots. The window contains ~300K tris, and renders at
around 27 fps (8.6M tris/sec) on my machine (1GHz P3, GeForce2Go).
The max pixel error is set at 2.5. Better video cards provide higher
framerate.
Other features:
Texture quadtree tiling: in the image above, the source texture is
32K x 32K texels. It's being rendered using vanilla OpenGL texture
calls, using a couple hundred active quadtree tiles which are each
128 x 128.
Background paging: the demo can work off of large geometry and
texture files on disk, only pulling in the pieces that are necessary
to draw a particular view. In the image above, the dataset
represents several GB of uncompressed data. The original
heightfield was 16K x 16K x 16 bits, plus the texture is 32K x 32K.
After preprocessing, it's about 500MB on disk (including JPEG
compression of the texture data), while the demo runs within about
100MB of RAM. Most of the paging work happens in a background
thread, to avoid hitches in framerate.
The code is all public domain, so you are encouraged to do whatever
you want with it. The precompiled demo runs on Win32, but the code
also compiles and runs under Linux. Try it out, and send me bugfixes!
The homepage of the project is:
http://tulrich.com/geekstuff/chunklod.html
There is more documentation there, and links to the downloads and
SourceForge project.
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