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OpenGL Brute force terrain on 10fps

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I use OpenGL to brute-force render a 512 x 512 terrain using triangle strips. For texture mapping I use a base 128 x 128 texture stretched over the surface and a 128 x 128 detail texture tiled all over the surface. Nothing fancy here. I use FRAPS and I get 10 fps. I think it's very low. What do u think I should do? The system is AMD 3000+, Geforce 6800 with 128 MB and 1 GB RAM. Thanks.

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Guest Anonymous Poster
1
make sure mip-mapping is enable for your textures
it really helps improve texture rendering time

2
quit using brute force, at the least cull the section of the heightmap that is clearly behind the camera...

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At least use an OCTree to cull out parts of the terrain that you cant see.
OCTree is a very simple space partitioning algorithm.

You can use ROAM (Realtime Optimally Adapting Meshes) very effectively to dramatically increase the FPS for terrains.

Use vertex arrays or vertex buffers to increase speed.

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Doing all those glVertex calls really slows down. My terrain rendering went from 40 fps to 300+ just by putting it into display lists. Of course you should further optimize with octree/quadtree and frustum culling, so you draw only what's visible.

-Riku

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If you're using glVertex (which I'm going to assume you are), that's not brute force. That's stupid force. Switch to VBOs and you'll be able to move vastly higher numbers of polys.

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How are you rendering it? Is the terrain stored in a VBO or a display list or whatever (in VRAM) or are you transferring it to the GPU each frame? Does the frame rate vary depending on how much of the terrain is in view?

Half a million polygons shouldn't be too much for a reasonably modern video card... You're only getting 5Mtris/sec which is a really low number indeed.

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I use glVertex() calls. It seems strange to me too because the rate is too low even for brute force that's why I made the post. I'll use VBO and some culling technique to see what happens.

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I just put my terrain rendering into display lists (added a compile function that compiles the display lists and does a few other things) and now my terrain render function is 4 lines long. However, it didn't seem to increase my framerate at all. I'm certainly not able to double the fidelity of the terrain, or the FPS drops from a constant locked 60 to about 30-40.

I also just stopped drawing parts of the terrain behind the camera, and saw no difference :S

Any suggestions?

[Edited by - industrion on October 10, 2006 1:07:24 PM]

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Quote:
Original post by industrion
I just put my terrain rendering into display lists (added a compile function that compiles the display lists and does a few other things) and now my terrain render function is 4 lines long. However, it didn't seem to increase my framerate at all. I'm certainly not able to double the fidelity of the terrain, or the FPS drops from a constant locked 60 to about 30-40.


what do you mean by "constant locked 60"?

I think in your case OpenGL is waiting for the VSync to complete before swapping the buffers. What it means is, if the frequency of your display mode is 60 Hz then you will get a max FPS of 60. You can turn off VSync wait in OpenGL if you want by using the extension wglSwapIntervalEXT(0) and your FPS should increase.

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Immediate mode (glVertex stuff) is very slow compared to any method of storing your vertices in VRAM. You're not only constantly sending data from your program to the GL driver which in turns sends it over to the GPU, but you're doing it just a few bytes at a time which is the most inefficient way possible. This is not at all utilizing the "brute force" of your video card, which is the capability to render a massive number of polygons in one go. Your card should be able to draw at least 100Mtris/s unless you run out of fillrate first.

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i did alot of testing about 12 months ago on rendering terrain's using brute force. My results showed the fastest way was using triangle strips and display lists. Using triangle strips and a static VBO was very close but on averages the dsiplay list always beat it. That was on ATI hardware and i never bothered on nvidia hardware. Arranging the data into triangles strips always beat arranging the data into a triangle list.
I was suprised because i thought the static VBO way would win hands down but it didn't. Also note i did not use any culling methods at all in my testing.

GeoMetrical Mip Mapping is still my favourite terrain algo, simple to implement and still works pretty good on modern hardware and is alot more CPU friendly than ROAM is. ROAM is very outdated and i would not recommend using it at all. Have alook at vterrain, they have a very good list of alot of different terrain algo's.

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I have another question:
Are all the framerates which are mentioned in forums measured without VSync lock?
Because if it is so, I put my VSync off from the driver properties and I finally used VBOs to render my terrain. I get maximum 57 fps. Isn't it too slow even for brute force? How much better will a culling techique do things?
Thanks

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Quote:
Original post by mits
Are all the framerates which are mentioned in forums measured without VSync lock?


Yes probably. If it is above 100 then surely.

FPS is one of the benchmarks that is used. If you are so concerned that your application is slow, profile it.

Quote:

I get maximum 57 fps. Isn't it too slow even for brute force? How much better will a culling techique do things?


Depends, but most probably they will speed up rendering. Every culling technique has its strengths and weaknesses. Be sure to read up on each one. Quadtree and Octrees work well with terrains and are probably the easiest to implement. There are others that are better. The choice is up to you. Understand what each technique does and don’t just blindly implement one just because some other “great” programmer has implemented it in his engine.

You can also effectively employ LOD (level of detail) algorithms on a terrain so that far off distant scenery can be rendered with less triangles. Read up on that too.

Optimize OpenGL calls. Read up on optimizations and FAQs on this site. Read read read.

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Depending on your method of texturing and the resolution you're running at, you could be fill rate limited. Does the framerate improve when the terrain takes up less of the screen, or if you run at a lower resolution with no anti-aliasing or anisotropic filtering? If not, then you may indeed be geometry limited and culling would help.

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