glBeginTransformFeedback

glBeginTransformFeedback is a function in the OpenGL programming interface. It is used to initiate a transform feedback operation. Transform feedback is a graphics pipeline feature that allows for the capture of geometry that has been processed by the vertex shader. Instead of rendering this geometry to the screen, it can be written back to a buffer object.

When glBeginTransformFeedback is called, the OpenGL state is set to begin recording the data streamed from the vertex shader. This operation requires that a transform feedback object be bound. The transform feedback object specifies which variables from the vertex shader's output should be captured and into which buffer objects they should be written.

The parameters for glBeginTransformFeedback include a mode, which specifies the primitive type that will be captured. Common modes include GL_POINTS, GL_LINES, and GL_TRIANGLES. After glBeginTransformFeedback is called, subsequent drawing commands will have their vertex shader output streamed to the bound buffers.

The transform feedback operation is typically concluded with a call to glEndTransformFeedback. Between these two calls, geometry is processed and its specified attributes are written to the buffer objects associated with the bound transform feedback object. This captured data can then be used for various purposes, such as for further processing in subsequent rendering passes, simulation, or for use by the CPU.