I was doubting: I'm writing a cross-platform engine OpenGL C++, I figured out Windows forces the developers to access OpenGL features above 1.1 through extensions.
Now the thing is, on Linux, I know that I can directly access functions if the version supports it through glext.h and opengl version. The problem is that if on Linux, the core doesn't support it, is it possible there is an extensions that supports the same functionality, in my case vertex buffer objects?
I'm doing something like this:
Windows:
#define glFunction functionpointer_to_the_extension
Linux:
Since glext already defined glFunction, I can write in client code glFunction, and compile it both on Windows AND Linux without changing a single line in my client code using the engine (my goal).
Now the thing is, I saw a tutorial use only the extension on Linux, and not checking for the opengl implementation version. If the functionality is available in the core, is it also available as extension (VBO's e.g.)? Or is an extension something you never know is available?
I want to write an engine that is capable of using all the hardware functionalities, so I need to check (on Linux) for extensions as well as core version for possible functionality implementation.
Best Answer
That sounds odd, because Windows have never forced me to use extensions, I always use core functions when possible, and while saying "when possible" I mean if my graphics card/driver supports the features. Because that plays the biggest part.
Not necessarily! But always favor the core functions when you can. Though when using extensions (EXT, ARB, etc) just always remember to check, if they are available.
If you're going to release a program using an NV Extension (Nvidia Extension), then again be sure to have something that checks whether the function is available, as if someone with a non-Nvidia graphics card uses your program it will most likely crash.
Yes, you never know for sure if an extension is available, it depends on various things such as.
By using core functions the chances are that the majority of people will be able to run the program, as long as their graphics card can run the particular GL version.
Remember
Always remember you can't mix-match and use
GL_TEXTURE1
withglActiveTextureARB
and you can't useGL_TEXTURE1_EXT
withglActiveTexture
. Even though mixing them sometimes produces the desired result, there is no guarantee for that.