And how does DX and OpenGL "make 3D exist"? I want to know how I can write a 3-D a library to render a 3-D world witg models. But any help? Thanks. Also, my main question.
closed as not a real question by Sean Middleditch, Maik Semder, Tetrad♦ Jan 2 '13 at 21:04
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OpenGL and Direct3D are what you can call low-level graphics libraries. They provide a very thin layer over manually sending data to the GPU, and are the basis of almost all other 3D graphics libraries.
Libraries that make use of OpenGL and Direct3D are more commonly considered to be "rendering engines", as they abstract away much of the code that interfaces with the GPU. Some notable examples of these rendering engines are:
There are countless others, but these are some of the most widely-used. They are more high-level, and are more suited to faster and simplified development rather than total control and performance. They are good enough for indie games if you don't want to spend a lot of time on writing your own rendering back-end.
If you value being able to do whatever you want with your engine without needing to work around the limitations of high-level frameworks, low-level APIs like OpenGL and Direct3D are for you.