GLMAPINVALIDATEBUFFERBIT

GL_MAP_INVALIDATE... refers to a family of OpenGL buffer mapping flags used with the glMapBufferRange function. They specify how the mapped memory may be treated by the driver and can enable optimizations for streaming or overwrite-heavy workloads. These flags are part of the ARB_map_buffer_range extension and are supported in modern OpenGL and OpenGL ES contexts.

GL_MAP_INVALIDATE_RANGE_BIT indicates that the contents of the specified mapped range are not required to be preserved. When used with glMapBufferRange, the driver may discard the previous contents of that range, avoiding the need to synchronize with existing data. This can reduce stalls when the application intends to overwrite only a portion of a buffer.

GL_MAP_INVALIDATE_BUFFER_BIT indicates that the entire buffer can be invalidated. This signals the driver that no existing contents need to be preserved, allowing more aggressive optimization and potentially eliminating unnecessary reads. It is particularly useful when the whole buffer will be rewritten.

Both invalidation flags are meaningful only when mapping with write access, typically in combination with GL_MAP_WRITE_BIT. They may be ignored on implementations that do not support the corresponding extension or feature set. They are not intended for use with read-only mappings.

GL_MAP_UNSYNCHRONIZED_BIT is a related flag that disables certain synchronization guarantees, allowing potentially lower latency at the cost of requiring the application to ensure there are no concurrent writes or reads by the GL. It is commonly used alongside the invalidation flags in advanced streaming scenarios.

In practice, these flags help optimize buffer updates by reducing synchronization and data traffic when the previous contents are known to be unnecessary. Availability depends on API version and platform support; consult the specific OpenGL or OpenGL ES specification for exact requirements and behavior. Examples of usage include glMapBufferRange(GL_ARRAY_BUFFER, 0, size, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_RANGE_BIT) and glMapBufferRange(GL_ARRAY_BUFFER, 0, size, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT).