glGetTransformFeedbackiv

glGetTransformFeedback: man4/glGetTransformFeedback.xml

In order to use the Transform Feedback functionality, you need to configure the Transform Feedback Buffer indexed bindings. This can be achieved by either using glBindBufferBase or glBindBuffersBase to associate whole buffer object storage to one of the Transform Feedback Binding Points, or by calling glBindBufferRange or glBindBuffersRange to use a region of a buffer object storage for the binding. You may want to (but are not required to) bind a Transform Feedback Object first, in order to cache the binding configuration. This usually allows you to restore the Transform Feedback configuration faster, than if you were to execute a list of API calls necessary to set up the Transform Feedback state of your liking. This reference page discusses two types of getters that operate on Transform Feedback Objects and their bindings. The first class operates on general Transform Feedback binding point and includes glGetTransformFeedbackiv function. glGetTransformFeedbackiv can be used to retrieve information about Transform Feedback object bound to the general Transform Feedback binding point, as configured with a glBindTransformFeedback call. In this case, you can check:

1. What the ID of the currently bound Transform Feedback Object is; ( GL_TRANSFORM_FEEDBACK_BUFFER_BINDING )
2. Whether the Transform Feedback process is currently paused; ( GL_TRANSFORM_FEEDBACK_PAUSED )
3. Whether the Transform Feedback process has been begun and is currently undergoing; ( GL_TRANSFORM_FEEDBACK_ACTIVE )

The latter class, which includes glGetTransformFeedbacki_v and glGetTransformFeedbacki64_v functions, can be used to check what the current configuration of each of the buffer object regions bound to Transform Feedback Buffer binding points is. This allows you to query for the following information:

1. glGetTransformFeedbacki_v only: What the ID of the Buffer Object bound to a Transform Feedback Binding Point of user-specified index is; ( GL_TRANSFORM_FEEDBACK_BUFFER_BINDING ).
2. glGetTransformFeedbacki64_v only: What the start offset configured for the binding is; ( GL_TRANSFORM_FEEDBACK_BUFFER_START );
3. glGetTransformFeedbacki64_v only: What the length of the region used for the binding is; ( GL_TRANSFORM_FEEDBACK_BUFFER_SIZE );