Hi, I'm playing with vertex buffer objects, and am comparing mapped buffer and client-stored buffers. For a mapped buffer, I call glBufferData() with NULL avoid sync problems, then I call glMapBuffer(), fill the buffer, then unmap it. It works perfectly, 390fps with a single textured quad on a Radeon X200M. For a client-stored buffer, I create a buffer (new float[foo]), fill it, then call glBufferData(). It works too, with more than 470fps for the same scene. On this scene, VBO is STATIC_DRAW, and of course, is never modified. I thought client-stored buffer was useful only for frequently modified datas, but it seems there are faster anyway. Does anyone knows why I should use mapped buffer, except to avoid datas in main memory ? Thanks.

I tested with the stanford bunny, 8100 tris, and have the same perfs (33fps on x200m), but this bunny has no index buffer, perhaps there's something related.

Anyway, I find this a bit strange.

Quote:Original post by Galdor
Hi,

I'm playing with vertex buffer objects, and am comparing mapped buffer and client-stored buffers.

For a mapped buffer, I call glBufferData() with NULL avoid sync problems, then I call glMapBuffer(), fill the buffer, then unmap it. It works perfectly, 390fps with a single textured quad on a Radeon X200M.

For a client-stored buffer, I create a buffer (new float[foo]), fill it, then call glBufferData(). It works too, with more than 470fps for the same scene.

On this scene, VBO is STATIC_DRAW, and of course, is never modified.

I thought client-stored buffer was useful only for frequently modified datas, but it seems there are faster anyway.

Does anyone knows why I should use mapped buffer, except to avoid datas in main memory ?

Thanks.

I don't think you really understand what's going on here. In both versions, you are not using client-side memory at all. When you unmap, data gets copied to some part of GPU-accessible memory. However, the same thing happens with glBufferData. Even more so, you can delete your own buffer (the one you allocated with new) immediately thereafter. In fact, I can't really explain the difference in framerate, but as darren_mfuk pointed out, one quad isn't really up to the test either. It could be pretty much anything, even external factors.

I use the term "client-side" to mark the difference with mapped memory, I know how vbo's content is stored.

For the drivers, they are Linux driver 8.35.5, I would'nt be surprized if they are clumsy (ATI+linux+mobile card = shit, nothing new).