OpenGL VBO within multiple threads

Question

I am developing a program in C++/OpenGL which draws terrain of the entire world. I have a database of altitude heights stored as tiles. Every time I start the program, a til

Answer 1

This is really not that complicated.

You just make two buffer objects: one that you're using for current rendering and one that you will be using in the future. When the unused buffer is full of data, the rendering thread switches to rendering from that one. The previously used buffer becomes the unused one.

You can upload the data in one of two ways. One way is for your data creation thread to create an array of data that the rendering thread will upload to the buffer object with glBufferData. Obviously this will require some synchronization, but it's sync code that you need: your render thread must ultimately be informed when data is ready so that it can render with the new data.

The other way is for your rendering thread to be told that data needs to start being generated. At which point, it will map the unused buffer object and pass the mapped pointer to the data creation thread. That thread will generate data directly into that mapped pointer. When it finishes, it informs the render thread, which will unmap the buffer and then render with the data.

Neither method requires multiple contexts or threading through OpenGL code.

Note that performance will be best served by not making the buffers bigger and smaller. Pick a size and stick with it; you don't want to resize buffers with glBufferData.