Triangle reduction in LODs (in practice).

Captian Goatse · 2003-08-18T02:26:02

I have started to play around with different kind of triangle reduction techniques and read a megaton of material concerning the topic. Papers are all great, however, they fail to tell me how to reduce triangles in practice. The common method around is to start from previous implementations and "modify" the code to suit your own purposes. Threads I've seen in past tend to go like this: "I want to implement level of detal x?" followed by answer "Yeah, clod is working really great for me, go for it d00d". "O wait what the papers don't give enough information..." Now, as far as I undestand, a method similiar to binary triangle trees is one of the best way to reduce the terrain. I understand how it works in theory, but in practice it is little bit harder especially when in implementation. BinTriTrees: -Should I calculate multiple levels of bintritrees for the terrain? -How do I incorporate them with the indices, so that there is an actual visible difference? -How do I make the keypoints of the terrain, such as hills to show, so that when I build my indices based on the reduced level data I know what points are truly visible? I'd still like to maintain a global array of vertices and only adjust the indices, since it seems to be the simplest way to go around. Indices: -Should I generate unique set of them for every "patch, or quadtree node"? Doesn't this turn into overkill memory wise? -Should I calculate them on the fly? I can't see this working. -Now the easiest and way to reduce triangles would be through adjusting the indices. This also seems to be the simplest so I will venture into this direction. I think I have the error adjustment down pretty well, after all thats 90% of the papers talk about. I'll now start to manually reduce the triangles of a small heightmap 20 x 20 and see what happens. The main way I'll adjust the triangles will be through the distance from the patch center to the viewers position. I see, I seem to be talking about some sort of clod algo. I guess I have to build indices only once for each subdivision level. [edited by - Captian Goatse on August 16, 2003 11:15:43 AM]

Graphics and GPU Programming Programming

Started by Captian Goatse August 16, 2003 09:44 AM

10 comments, last by Captian Goatse 20 years, 8 months ago

Captian Goatse

122

Author

August 17, 2003 12:59 PM

Now I have a final problem. I can't seem to get the right distance from the center of the node to the position of camera.

The behaviour is extremely wierd, since I have higher detail on the side closer to the origin and lower on the further side. In fact it is frustratingly nasty.

I'm using displacement = cam.pos - node.center

and then getting the unsquared length. And thoughts on what I might be doing wrong?

Edit: Well final and final, I have to fix the cracs after that and it should be relatively easy.

[edited by - Captian Goatse on August 17, 2003 2:00:49 PM]

HellRaiZer

1,001

August 18, 2003 02:26 AM

If you are using the unsquared "distance" try to take the absolute value of the difference.

distance = fabs(camera.pos.x - node.center.x) + fabs(camera.pos.z - node.center.z)

HellRaiZer

HellRaiZer

Triangle reduction in LODs (in practice).

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Triangle reduction in LODs (in practice).

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