Vertex buffers, using glut

Hi,

I'm trying to work out how to use vertex buffers using the 
GL_ARB-vertex_buffer_object extension.  I have been working in linux 
using glut, but trying to stay as portable as possible.

Anyway, I'm trying to work out how to load the functions needed.  There 
are lots of web resources on how to do it using SDL library, but I can't 
find how to do it without using SDL.

I thought I could use glutGetProcAddress(...), but on one linux setup it 
said 'glutGetProcAddress' undeclared even though I included <GL/glut.h>.
I also was not sure what type it would return.

I see in Windows it's something like
PFNGLBINDBUFFERARBPROC glBindBufferARB = (PFNGLBINDBUFFERARBPROC) 
wglGetProcAddress("glBindBufferARB");

If I just use glXGetProcAddress, can I do something similar?  What do I 
use as the return type (instead of PFNGLBINDBUFFERARBPROC)?

Thanks for your help.

Yes, that's what you need to use.


PFNGLBINDBUFFERARBPROC is defined in "glext.h"
which you can get here:

 http://www.**--****.com/ 

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Tried glew? See  http://www.**--****.com/ 

Thanks for your help.  Now I'm doing something like this:

PFNGLBINDBUFFERARBPROC pglBindBufferARB = NULL;
pglBindBufferARB = (PFNGLBINDBUFFERARBPROC) 
glXGetProcAddress("glBindBufferARB");

I hope this isn't a stupid question, but I'm getting an error due to an 
"invalid conversion from `const char*' to `const GLubyte*'.  How can I 
prevent this?  Casting didn't seem to work :/

Also, I noticed in glext.h that the function glBindBufferARB is already 
defined.  Is the above still necessary?  I'm a bit confused as to what 
the glXGetProcAddress is doing.  The way I understood was this was to 
load the function that may be defined by the drivers.. I assume it is 
necessary in non-Windows implementations.  The glBindBufferARB function 
didn't seem to work if I called it directly.

If I can't get this going, I might try GLEW - it looked quite good.

Thanks again.

Dunno. Ask the people who wrote your compiler...


No it isn't. There's a function prototype but that's
not the same thing. You still need to have your own
pointer somewhere in your program.


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GLubyte is usually a typedef for unsigned char.


Hmm, on my Linux box, I can use it directly. The problem about that is that
your program then will only run if the OpenGL library actually supports
that extension. If you try other ones, you'll get a linker error. To
prevent this, you don't call the function directly, but instead try to get
a pointer to it and only call the function through that pointer. In this
case, the linker isn't involved, so your program will still link if the
function isn't provided, so it can contain a fallback solution for OpenGL
implementations that don't support the extension.


It is.

Thanks again guys.  I solved the GLubyte* problem, for some reason it 
worked with casting if (and only if) I stored the intermediate result as 
a GLubyte* and then used that.

I'm getting closer.  However, I now have a linking problem.  Although it 
compiles fine, I get an error when linking saying "undefined reference 
to `glXGetProcAddress'".  I was thinking this might be due to missing 
glx libraries?  I am using '-L/usr/local/lib -lGL -lGLU -lglut 
-L/usr/X11R6/lib'

Any ideas?

Order is important. Try -lglut -lGLU -lGL
jbw

Thanks for the help, but I still get the error.

Thanks for the help everyone, I have solved the problem by using 
glXGetProcAddressARB (was using glXGetProcAddress before) - and by 
defining GLX_GLXEXT_PROTOTYPES.

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What compiler are you using?  doing 'glXGetProcAddressARB( (const
GLubyte *) "foo" );' shouldn't generate any compiler warnings or errors.


Depending on how old your libGL is, you may need to use
glXGetProcAddressARB.
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