glUnmapBuffer

glUnmapBuffer is an OpenGL function used to unmap a buffer object that was previously mapped with glMapBuffer or glMapBufferRange. The only parameter is the target, which identifies the buffer binding point (for example GL_ARRAY_BUFFER or GL_ELEMENT_ARRAY_BUFFER). The exact set of valid targets depends on the OpenGL version and extensions in use.

The function returns a GLboolean. If the unmapping succeeds, glUnmapBuffer returns GL_TRUE and the data store contents are preserved for use by OpenGL. If the unmapping fails, it returns GL_FALSE and the contents of the buffer become undefined; in this case the application should not rely on the data and may need to re-upload or reinitialize the buffer contents.

Error handling and states: GL_INVALID_OPERATION is generated if there is no buffer bound to the specified target, if the bound buffer is not currently mapped, or if the buffer object cannot be unmapped in the current context. In addition, when using advanced mapping modes such as persistent mappings, glUnmapBuffer plays a role in finalizing the access to the data store and making it available again to the GL pipeline.

Usage notes: glUnmapBuffer is typically called after the application has finished reading or writing to a mapped buffer region. It is a synchronization point that indicates the CPU-side modifications are complete and that the GPU may access the buffer data again. If a mapping was done with special flags that allow persistent access, the unmapping step may have nuanced behavior depending on the context and extension setup. Related functions include glMapBuffer and glMapBufferRange.