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d000hg

VERY low poly models

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I''m thinking about trees, boulders, fences etc in my terrain engine. Obvoiusly with thousands of things, low poly models are a must. For fences I thought just a texture upright on the ground, running along the ground. Trees could be billboards, but I saw a nice thing with two 2d images at right angles (like how you slotted two cut-outs of a tree together to get a 3d one when you were a kid). This lets you get a 3d model for only 4 polys, and the extra overhead with rotating billboards surely makes this quicker. How about boulders - just standard 3d models maybe?
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John 3:16

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Opinions? Like whether that''s a good idea, or if you know something better?
Or how to get the simplest models you can get close to - I''d quite like to be able to drive through a forest, or have to avoid big rocks. But I don''t want a tree to be thousands or even hundreds of polys If possible.



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John 3:16

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Using two static polys at 90 degrees will probably look fine far away, it''s used often in games, but up close will look pretty bad if the user has the time/inclination to examine them at all (if they''re whizzing by at 300mph they''re not too likely to notice though).

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Any easy way to have reasonable trees easily? Procedurally generated randomly would be good, but how does that make the branches join smoothly - plus high poly count and too slow to do at runtime I''m guessing?
Also how would you blend from a very simple model for far away to something detailed for up close without getting ugly jumps?



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John 3:16

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quote:
Original post by d000hg
Also how would you blend from a very simple model for far away to something detailed for up close without getting ugly jumps?


You could make transitions between the models using alpha blending or morphing. Do a smooth interpolation between the two levels of detail over some range of distances from the viewer (if you''re doing a simple distance based LOD).

For example if you want to alpha blend the two models linearly, with a high LOD at 200 units away and low LOD at 250 units away, and the object is at distance 200 < X < 250: Draw the low LOD model at (X-200)/(250-200) transparency and the high LOD model at 1-X transparency. This will produce a smooth, linear transition between the high and low LOD. You could easily modify this procedure to produce a non-linear transition

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Guest Anonymous Poster
Dobbs, maybe I''m misunderstanding, but wouldn''t that create a medium-range area where it would be slower than either close up or far away since it''s drawing both the high AND the low detail models, AND alpha-blending between the two?

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Using LOD models is based on the premise of, "If you can''t see the details, why have them at all?".
You should not see LOD changes, models should be switched when the changes are not generally noticable. The more models you switch through, the less chance of anyone noticing anything at all.

You could also include a LOD setting, where the lower it is the less distance it takes for switches, if it gets really close it just doesn''t bother with the high poly models at all.

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