GLSTREAMDRAW

GL_STREAM_DRAW is a usage hint used with OpenGL buffer objects. It is one of the practice patterns passed to glBufferData and glBufferSubData to describe how the application intends to use the buffer’s contents. The GL_STREAM_DRAW value indicates that the data store will be modified once and used at most a few times for drawing.

In practice, GL_STREAM_DRAW is chosen for buffers whose contents are updated frequently and then used a limited number of times, such as streaming vertex data or transient buffers that change each frame. The specification suggests that such data may be stored in memory optimized for streaming access, and that the data may not be retained in GPU caches for extended periods.

Performance considerations for GL_STREAM_DRAW depend on the hardware and driver implementation. It does not guarantee avoiding stalls or that data will remain resident in GPU memory. A common technique after updating a buffer is to orphan its previous storage by calling glBufferData with a NULL pointer and then uploading new data, which can reduce or avoid synchronization delays.

GL_STREAM_DRAW is part of a family of usage hints that also includes GL_STATIC_DRAW and GL_DYNAMIC_DRAW, each describing different expected patterns of modification and use. The choice of hint guides the driver in memory placement and caching decisions and should reflect the intended data update frequency and draw usage.