Hmm.. Mars, it is kinda hard to answer without more specifics, although I think you may not be considering the problem correctly. You can also have "as many triangles in a 1 by 1 square" with triangle strips, just start creating vertices in between?! By "chaotic" do you mean, not existing within a regular grid? Because that is the only reason I could see that triangle fans would have an advantage over strips. I'm assuming your heightmap is evenly spaced (is a regular grid), in which case you need to think about how to render triangle strips with more (smaller) triangles, rather than how you are rendering the triangles themselves. Remember that both fans and strips are just a shorthand way of specifying triangles...


regards,
darren

In general, you'll get just as good performance (if not better) with indexed triangle lists instead of the more awkward strips or fans.

well, i'm still a little confused as to what you mean by 'chaotic'. do you mean, a lot of variation in height, in other words, you are getting crappy looking 'stair-step' artifacts where there is a lot of variation? if so, then sorry for misleading you, but adding vertices is probably not going to help. unless you have some method of adding detail to your heightmap (simple bilinear interpolation, fractals, etc - some way of adding unique height values in between the values of your height map), you are just going to get smaller, but still flat and bad-looking, triangles. you should look into either increasing the heightmap resolution (in other words, increase the heightmap width + height but keep the 'interpreted' size the same, using the extra points as data in between), or perhaps using something besides bytes to store the height values. with only 255 possible height values, you are going to get really bad looking artifacts on anything with a lot of variation. i use unsigned shorts, which are fine for me, although you could even use floats and not worry about accuracy problems at all.

@OrangyTang -
sorry, but i'd have to disagree. i use indexed triangle strips in my terrain renderer, and it's a lot better for two reasons - faster, because the index lists are shorts and quicker to traverse; and smaller, because I need roughly 1/3 the number of indices to represent the same terrain, which is REALLY important once you start looking into large (>1024) heightmaps..
*edit* well i guess i stand corrected on the speed of strips vs individual triangles, as phantom pointed out.. although i would still probably put more weight into memory consumption than which method might be faster on some cards, i guess it depends on what you're trying to do..

but, as far as you are concerned, MARS_999, he is probably right, you shouldn't be worrying about strips or fans yet, just get your heightmaps looking nice with regular triangles first, its easier, and there isn't anything special you can do with strips + fans that you can't with regular tris.

darren

[Edited by - darrenf on August 27, 2004 2:41:28 PM]

Fans will probably introduce more trouble than they are worth. The way I see it you can do one of 2 things with these fans in a grid and both have flaws.

1: You can have the fan radiate from a corner in each grid unit, which is just as limiting as the previous method unless you can have as many vertices as you want in each grid square, which would require something other than a simple heightmap and be very dificult to line up smoothly with the surrounding grid units.

2: You can have the fan radiate from the center of the grid unit, being slightly less limiting, but as I see it, even more difficult to line up smoothly (in most cases immposible.) so it falls back to being just barely less limited than 1. Oh, and you'll still need that new map format :)


I think your best bet is to possibly increase the size of your heightmap, and reduce the size of your grid units. Then to get the speed back up you'll need to look into LOD algorithms.