OpenGL texture upload using PBOs?

Question

I'm developing an OpenGL application using OpenGL2.1 and want to upload textures via threads.

What I have done so far:

1. Create a second context and share between the two
2. Upload texture data in a thread

Everything is working fine, except that I notice a small "lag" when the texture upload happens! I know this is because the driver have to synchronize the two contexts. The problem is that I want it to stream the texture. I don't want to update the texture later. I just want to load textures in the background while displaying an "almost smooth" loading animation without stalling the whole application.

That's the point I searched and found that PBOs can be used for DMA data transfer of pixel data. Is it possible to use a PBO for texture upload? If so, how?

Answer 1

You don't need a second context to upload the texture data async. Just make sure you don't use the buffer right after triggering the upload, or it will stall waiting for the copy to finish.

Here's an example of this process: http://www.songho.ca/opengl/gl_pbo.html#unpack

And here's a bit more info about what PBOs are and how they should be used: http://www.opengl.org/wiki/Pixel_Buffer_Object