Download rapids.zip

This is a model of a fast flowing river, similar in concept to the waterfall model but on a larger scale and more specific design. Honestly it’s more abandoned than finished, but I think there’s two useful features to it. One is that you can drop it into a map, build a valley around it and it still looks quite cool. The other is that it is an example of how to make a really large model – it’s over 2000 units in length and there was a technical hurdle to clear.

Originally this model was an experiment paired with a model of a river valley which had a specially designed texture to fake “alpha blended terrain”. There was a serious rendering issue in winquake with this setup. The software engines have approximations in their rendering code for .mdl triangles which work well as long as the triangles remain small within the viewport. The huge scale of these models ruins that, and the result was an extremely wobbly cliff that was nausea-inducing to view. So the geometry cliff had to go, but the water gets a pass because a) the low viewing angle that the player sees it from close up reduces the impact and b) because the water is moving and plausibly might ripple the effect is not so detrimental.

The model includes all the scripts to build it from the original md3
file. md3 format has a limit on the dimension of models, which cannot
exceed 512 units. mdl files can be built on any scale representable by
floating point numbers. So what we do is make the river at 1/4th scale,
translated within the standard md3 bounding box. Then the last few lines
of water.py scale the model up and translate it into place.

Please also note that the animated gif above drops half the frames from the animation and the full model has smoother motion. Also the usual tricks have been employed to ensure that the model is fully interpolation friendly.


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