Project Home
Project Home		 Documents
Documents		 Wiki
Wiki		 Discussion Forums
Discussions		 Project Information
Project Info
Graphics/Discussion/OpenGL ES/VBO and VA limits/List of Posts
Forum Topic - VBO and VA limits: (3 Items)
   
Update
Mike Gorchak
05/06/2009 10:14 AM
post28810
VBO and VA limits   
if VBO is activated in the current context, it doesn't check if offset passed via glVertexPointer() is exceeds amount of
 data passed to vertex buffer object.

glBindBufferOES(GL_ARRAY_BUFFER_ES, nVBOVertices);
glVertexPointer(3, GL_FLOAT, 0, 0x60000000);
glDrawArrays(GL_TRIANGLES, 0, nVertexCount);

It is silly example but in my case I specified 32768 vertices offset instead of 31255, and it was enough to hang all QNX
 box.

What is vertex maximum count (or memory size in bytes) limit when vertices  are passed to VBO ?

What about limits for VAs ? On devg-extreme2 glGetIntegerv() returns 65536 for GL_MAX_ELEMENTS_VERTICES and 
GL_MAX_ELEMENTS_INDICES. But by mistake I've passed near 98K of vertices and all primitives have been drawn, like there 
are no any limits.
Etienne Belanger(deleted)
05/07/2009 9:21 AM
post28891
Re: VBO and VA limits   
glVertexPointer can return one of the following errors:

GL_INVALID_VALUE is generated if size is not 2, 3, or 4.
GL_INVALID_ENUM is generated if type is is not an accepted value.
GL_INVALID_VALUE is generated if stride is negative.

The only VBO related work that glVertexPointer is required to do is to copy the buffer object name in the 
ARRAY_BUFFER_BINDING internal state to the VERTEX_ARRAY_BUFFER_BINDING internal state. This allows the following code to
 work:

glBindBuffer(GL_ARRAY_BUFFER, vbo);
[...]
glVertexPointer(3, GL_FLOAT, 0, 0);
[...]
glBufferData(GL_ARRAY_BUFFER, size, data, GL_STATIC_DRAW);
[...]
glDrawArrays(GL_TRIANGLES, 0, count);

GL_MAX_ELEMENTS_VERTICES and GL_MAX_ELEMENTS_INDICES are marked as exposed, but not queriable in the OpenGL ES 1.0 spec.
 Neither are exposed in the OpenGL ES 1.1 spec. For these reasons, I would just refrain from writing code that uses 
these constants.
Mike Gorchak
05/07/2009 9:59 AM
post28910
Re: VBO and VA limits   
> glBindBuffer(GL_ARRAY_BUFFER, vbo);
> [...]
> glVertexPointer(3, GL_FLOAT, 0, 0);
> [...]
> glBufferData(GL_ARRAY_BUFFER, size, data, GL_STATIC_DRAW);
> [...]
> glDrawArrays(GL_TRIANGLES, 0, count);

I'm talking about bad offset value could hang the machine. I know how to use VBOs.

Etienne, could you answer on question "What is maximum vertex count could be passed as VBOs and VAs data ?"

Return


  A subsidiary of BlackBerry             All content ©2004-2013, QNX Software Systems