CODEWITHSUNDEEP
opengl
BЈовић
BЈовић

Reputation: 64253

What is a query object in OpenGL?

I have found glBeginQuery function in the OpenGL SDK.

So, what is the query object and how is it used?

Upvotes: 2

Views: 1845

Answers (2)

tibur
tibur

Reputation: 11636

Look at occlusion query. It allows you to retrieve the number of fragments drawn.

A common usage for this extension is to draw bounding boxes of objects while color and zbuffer is in read only mode. Then, thanks to this query object you get the number of fragments that the bounding box would have drawn. If that number is bellow a certain threshold, you don't draw the corresponding geometry. That allows you to cull parts of the scene that is hidden by other objects (but still inside the frustum).

Upvotes: 3

Martin Beckett
Martin Beckett

Reputation: 96139

It's used to query properties of the object in the scene, eg. is it occluded

http://www.opengl-doc.com/Sams-OpenGL.SuperBible.Third/0672326019/ch17lev1sec3.html

Upvotes: 2

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