Re: [Haskell-cafe] OpenGL Speed!

If you still want to use glVertex with GL_POINTS, instead of a display list, you'd better go with vertex array or VBO. But still, if the implicit coordinates of a raster is assumed, pairing the coordinates with their value is overkill. Cheers, Thu 2010/7/29 Job Vranish :

Yeah, using openGL Points to draw 2D images will probably be pretty slow. However, if you don't need to change your points every frame, a display list might improve the speed quite a bit (you could still transform the points as a whole).

Also, you could try the SDL bindings for haskell: http://hackage.haskell.org/package/SDL SDL is better suited for 2D drawing (IMHO). http://www.libsdl.org/

- Job

On Thu, Jul 29, 2010 at 6:51 AM, Vo Minh Thu wrote:

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2010/7/29 Eitan Goldshtrom :

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I'm having an unusual problem with OpenGL. To be honest I probably shouldn't be using OpenGL for this, as I'm just doing 2D and only drawing Points, but I don't know about any other display packages, so I'm making due. If this is a problem because of OpenGL however, then I'll have to learn another package. The problem is speed. I have a list of points representing the color of 800x600 pixels. All I'm trying to do is display the pixels on the screen. I use the following:

renderPrimitive Points $ mapM_ display list flush where   display [] = return ()   display ((x,y,i):n) = do     color $ Color3 i i i     vertex $ Vertex2 x y     display n

But, for some reason this takes FOREVER. I don't know how to use debugging hooks yet without an IDE -- and I don't use an IDE -- but I used a cleverly placed putStrLn to see that it was actually working, just really really slowly. Is there a solution to this speed problem or should I use a package that's more suited to 2D applications like this? Also, if I should use another package, are there any suggestions for which to use? Thanks for any help.

Hi,

Although you can use Vertex* to put a single Point on the screen, it is not meant to be used as some kind of setPixel function.

If your goal is simply to set pixels' value of a raster, you can still use OpenGL but should use a single textured quad (and thus manipulate the texture's pixels).

There other possibilities to deal with raster graphics: - Use gtk; i.e. something like http://hackage.haskell.org/package/AC-EasyRaster-GTK - Output the data in some image format (if you want to do it yourself, the most simple is PPM) - Use X11 directly (if you're on unix) - ...

HTH, Thu _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe