Re: [Algorithms] VDPM vs ROAM

[Mark D. <duc...@ll...>]

Kevin,

It depends on how much effort you put in on each.  ROAM is easier to
get going for height maps, and is theoretically faster when you completely
optimize the mesh each frame.  Hoppe describes an idea of partially
optimizing in sweeps over the output mesh, so that a complete
optimization happens over the coarse of say ten frames.  ROAM
automagically takes advantage of frame-to-frame coherence to
get the best quality in your time budget, and take time proportionate
to the number of LOD changes.  ROAM thus gives you the best possible
quality in minimum theoretical time, whereas VDPM can cause
uncontrolled errors (example: you suddenly put your nose
right on top of some interesting geometry and it takes
a full second to pop to full detail).

I'm happy to give lot's of implementation details/suggestions
to you or anyone else who wants to give ROAM a try.
There are a number of other sources of information on various
approaches to ROAM-like systems out there (Alex Pfaffe
http://ddg.sourceforge.net/, Seumas McNally
http://www.longbowdigitalarts.com/seumas/ for example,
Ben Disoe has a good page http://vterrain.org/LOD/published.html).

Kevin Lackey wrote:

> Which algorithm is a smaller O. VDPM or ROAM. I am looking at fractally
> creating a height map for an entire planet and would like to know which of
> the two common terrain techniques is less computationally intense.
>
> Kevin
>
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