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Genesiiis

OpenGL OpenGL Basics

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Hi, I posted the following on the beginners forum but no one replied and I presumed it was just a bad place to post so im reposting here, thanks! ----------------------------------------- Hi, I just wanted to make sure that the way I understand the OpenGL API is correct. As I understand it, OpenGL is an API that provides accesability to 3D accelerated hardware. The OpenGL API uses the header gl.h in C++ and provides many functions, and there are also other libarys close to OpenGL like the OpenGL Utilities Libaray. Presuming that what I said there was mostly if not all correct, then comes the extentions. In my mind these are just basically add ons to the standard OpenGL libaray version. From what I have heard, some extenions get added to the OpenGL Libaray as new versions come out, but for the rest of the extentions they can be included in code through the use of other header files. Then the extensions provide more functions that can be used, such as the windows extention for win32 to Opengl, one of the function which is provides is wglCreateContext();. Thanks! -----------------------------------------

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The real reason why no one responded: you didn't give them any time. You waited one hour before reposting. Wait a day. Or two. Then try bumping your last post.

Also, asking a more specific question usually helps. You barely have a question in your post.

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I think you understand the OpenGL API correctly (as far as I know).

The extensions basically extend the OpenGL API, like you said, in order to let the hardware vendors (ie. nVidia/ATI) support features in their video cards that are not yet a part of the OpenGL API, mostly. Some extensions are not hardware specific (like ARB_ and EXT_ ones) and if they're usefuly, they usually get integrated in the core OpenGL API with time.

For example, before OpenGL 2.0 came out, ATI_fragment_shader was an extension that enabled you to perform the pixel shader v1.4 operations on an ATI Radeon 8500+. ARB_multitexture was there to enable multitexturing (which wasn't a part of the standard OpenGL API at the time; I'm not sure if it is now in the newer versions).

Hope that helps.

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Thanks, sorry about reposting quickly, all other threads I have started get responses in the first 5 mins or so, I wasnt trying to be impatient and I am very sorry about that. I have read over the nehe tutorials but the problem I find is that it does go though the theory of the functions, but not in depth enough, and I dont have any other API experience so although they are great tutorials I had to find more stuff all over the net and then peice it all together, thanks everyone!

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Quote:
Original post by Genesiiis
I have read over the nehe tutorials but the problem I find is that it does go though the theory of the functions, but not in depth enough

Well the new NeHe lessons being worked on does explain a lot more in detail what is actually going on.
Take the blending lesson as an example, the difference from the previous lesson could be a minimum of 3 lines (and it is near that in the original lesson) but the new blending lesson goes in depth on how to do things and exactly how it works in both a technical and simplified way, and instead of showing only one blendfunc we are showing the six most common ones + some hints about glBlendEquation.
All in all i really wish that we could release it today (it's really that much better), but it's not done yet.

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Well that sounds great, I am a big fan of the tutorials and dont get me wrong or anything, in no way can I critisise them in any way, I couldnt write them a 10th as good as they are now, anyway, thanks everyone!

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