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disable padding for VBO?

Started by Bow_vernon Oct 22, 2011 at 5:24 PM 3 replies 1.2k views

Original Post

Oct 22, 2011 at 5:24 PM

Hi I'm learning to use VBO (again) now, as I never had time to learn on that one. I wonder if I should disable padding in my custom vertex structure for the VBO to work....something like


 #include <pshpack1.h>
 //blah blah vertex structure
 struct MyVert
 {
 float u1,v1;
 float x,y,z;
 };
 #include <poppack.h>

I know the compiler would pad the structure otherwise, but will the opengl work fine with it? thanks before

Brother Bob

Oct 22, 2011 at 6:21 PM

That structure won't contain any padding, and even if a structure contains padding in general, the padding will be beneficial for the VBO as well. Removing the automatic padding costs you unaligned memory accesses, which may be bad for the VBO as well.

21st Century Moose

Oct 23, 2011 at 12:44 AM

As always, until you've definitively proven that it's a problem, don't do it. When you're learning something new is not the time to start complicating things by introducing optimizations, even optimizations that are not of dubious benefit. You're introducing too many variable factors, and if something goes wrong you're reducing your chances of being able to fix it (and of understanding what went wrong). Learn VBOs first, learn how to use them properly, then worry about lower level stuff.

Bow_vernon

Oct 23, 2011 at 9:19 AM

wow ok, I'll just start writing some code. Thanks guys, I'll come back when I got some problems

V-man

Oct 23, 2011 at 11:19 AM

http://www.opengl.org/wiki/Vertex_Buffer_Object
"ATI suggests that you align your vertex size for 32 bytes, so I added 4 floats to make it 2 * 32 bytes. For nVidia, I think it doesn't matter"

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