Portal:OpenGL Objects/Query Objects

A Query Object represents certain kinds of state, where accessing the state directly would improve severe synchronization problems. Query objects thus represent a result that is not necessarily available yet. Many of these queries are based on rendering operations that happen within a certain defined boundary.

There are a number of types of queries. There are queries for how many samples in a particular rendering operation passed all of the various post-fragment processing tests and the Fragment Shader itself. That is, how much of a rendered object is visible (if any). There are queries for how long the GPU took to execute some set of commands. And there are queries for how many primitives were written by a Transform Feedback operation.