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Submitted by Flavien Brebion, posted on May 01, 2003




Image Description, by Flavien Brebion



Here are two images of a "small" terrain renderer that i've been working on for two weeks now. It's going to be used for a procedural planet renderer, and features:

- A mix of earth heightmaps for high-level informations (up to the kilometer level), and on-the-fly computed procedural details for high frequencies, based on a 12-octaves ridged multi-perlin noise function.

- The current sample is 2048x2048 km with a resolution of 10m, which, if it was statically stored, would represent a bit more than 83 billion triangles. This means you can walk or fly for hours and never see the same thing.

- Uses geomorphing on the cpu, calculates lighting & textures on-the-fly. Texturing has to be improved, it uses two textures (grass and rock) using per-vertex blending at the moment.

- No cracks, T&L-friendly. The current shots run at a bit more than 100 fps (12 Millions of triangles per second) a on Radeon 9700. Polycount is in the 20k - 50k range per pass.

- CLOD is used with 5x5 chunks (instead of the 3x3 basic implementation). This helped to reduce the number of chunk nodes in memory at a given time, generally 1500-2000 in these screenshots. As a result frustum culling is pretty fast (2 ms average) and memory usage is pretty low (around 60 Mb).

- No standard distance culling: you can zoom seamlessly from the meter level up to many kilometers. Horizon culling is planned.

- Atmospheric effects, based on the paper from ATI: "Rendering outdoor light scattering in real-time". I use texture maps instead of vertex shaders though.

- The whole terrain is rendered in 3 pass: the first one is the unlit, textured terrain. The second pass does lighting modulated by the exctinction term. The last pass adds the in-scattering contribution. The sky is a sphere.

- TODO: better texturing (up to 6 layers), water rendering with env-bump-mapping, volumetric clouds + cloud shadows on the terrain, rain & snow, bump-mapping, earth curvature + horizon culling, misc. optmizations, and mostly, ground details (grass, rocks, trees).

For infos or questions, mail me at: f.brebion@vrcontext.com


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