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Kranomano

OpenGL Pixel output in OpenGl?

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Kranomano    122
Im willing to bet this has been asked before, but how would I write an RGB value to a specific x and y screen coord in OpenGl? Please give me some code, maybe a function like PutPixel(int x, int y, float r, float g, float b) or something. Thanks

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Bleakcabal    122
for color use glColor3f and use float value, if you don''t like them, get use to them, if not I think you can also use glColor3i or something like that, for specifics go here http://www.eecs.tulane.edu/www/graphics/doc/OpenGL-Man-Pages/opengl_index_spec.html is as all the OGL functions. To position your pixel use glTranslate3f and then use glBegin(GL_POINTS) you can set the point size with a function , just look at the functions list on the site I mentioned you should find it.

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Kranomano    122
You know what? Never mind. From what Im hearing, glDrawPixels is way too slow for what I want to do... I'll just use DX. Thanks anyway.

Edited by - Kranomano on January 26, 2001 8:56:46 PM

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Jansic    251
The way to draw single pixels effectively is, as previously mentioned) to use the ''GL_POINTS'' primitive (with antialiasing off and a 2D ortho projection).
To draw batches (rectangles) of pixels you can use glDrawPixels, also mentioned previously (though a textured quad will generally give better performance).

However - I''d say that if you have an intention of writing very many single pixels to the GL framebuffer then either your design is at fault or you''ve chosen the wrong API.

Jans.

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zedzeek    528
>>You know what? Never mind. From what Im hearing, glDrawPixels is way too slow for what I want to do... I''ll just use DX. Thanks anyway<<

what exactlly do u wanna do.

question: why was direct access (ie directdraw) to the frame buffer dropped in directx8

answer: cause it causes major slowdowns

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Kranomano    122
I was planning on making a 2d library, like the turbo graphics library from the turbo c++. Just some handy, easy way to do 2d gfx without a bunch of work. I do stuff like that a lot...

Im familiar with OGL, thats why I wanted to use it, but I''ll just learn a little DX for it.

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zedzeek    528
maybe u wanna have a look at SDL
http://www.libsdl.org/

supports directdraw under windows as well as opengl.

quite a few programs have been written using it eg for linux simcity 3000 , tribes2 , quake3 , deus ex
etc

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