vertex array vs display list Just Talk

Jonathan Medders · 2001-07-24T05:05:28

i know how to use either method fairly well, but here is my delima. I want to try a terrain engine, so i lay out a grid or floats like float terrain_height[100][100]; I then write up some algorithams for slopes and hills or what not, but i get stuck on drawing the data. I could simply use a quad or triangle strip, but i need to stick it on a display list to get good speed out of it, but i want the terrain to be deformable too, so a display list is no good. I cant figure out how to do a 2d array with vertex array, also, vertex arrays require that the vertex info is either 2 3 or 4 elements. I had the idea of stringing the whole thing into one long array, but that seems a bit complex. Im not out to make a visually stunning game(im only going to use simple models and small textures), so do i have the compute time to spare, and just use a strip. or is there some way to change data in a display list? or is there a different way of drawing that i have missed?

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Started by Eber Kain July 22, 2001 04:46 PM

11 comments, last by Eber Kain 22 years, 8 months ago

Shag

122

July 24, 2001 12:45 AM

what about using wglAllocateMemoryNV ... which i beleive allocates AGP memory in many cases. this should vastly improve vertex performance, because the graphics card can DMA the data from the memory ... although i guess that that only works for NV cards - but maybe other vendors have a similar function.

I maybe wrong there, i have only just discovered that particular function, and haven''t relly looked into it yet ... just a thought though

Eber Kain

130

Author

July 24, 2001 02:09 AM

Vertex arrays draw fast because they cache the vertex data in the cards memory as long as possable, and any duplicate calls to the same vertes are not repeated, just pulled from the cached ones. Like if i was just drawing quads for my terrain every coord would be supplied 4 times. With a strip every coord is supplied 2 times.

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avianRR

100

July 24, 2001 05:05 AM

quote:Original post by Eber Kain
If you are drawing it as triangle strips, then your not useing a vertex array are you. I mean you may have an array of vertices, but your not drawing it with glDrawElements(); or anything.

Yes I am!

here''s how...

glDrawElements(GL_TRIANGLE_STRIP, 2*Width, GL_UNSIGNED_INT, &trianglestrip[0]);

Something else that I learned is that depending on the video card, drivers, display mode, etc... the efficency of using vertex arrays or display lists or the two together was different. But generally vertex arrays were the way to go with display list being a close second and putting a vertex array in a display list provided horible performance.

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vertex array vs display list Just Talk

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