How can I use glReadPixels to select object in the scene?

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I want to use glReadPixels() to select object in the scene. I gave every object in the scene a different color, but when I use the gluLookAt function to change the view, the glReadPixels() can not get the right color of the object my mouse click, Why? If I don't move,It can select the object my mouse click.:confused::confused:
I find that when I move the view,I click mouse at the same at same spot,then the object is selected which was I didn't move view before.
The object selected is not the object which my mouse click now.:confused:

Posted 14-Jun-10 22:17pm

thundersun

Updated 16-Jun-10 16:55pm

v4

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Anthony Mushrow · Answer 1 · 2010-06-15T02:48:00

Solution 2

In windows (I'm assuming your using windows) the origin (0,0) is at the top left of the screen, but with glReadPixels the origin is at the bottom left so you may have to adjust the mouse coords before you use them with the function.

Also you may want to do something more like this:
Picking Tutorial[^]

It's more effort but it would allow you to pick between objects of the same colour.

Posted 15-Jun-10 2:48am

Anthony Mushrow

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thundersun 15-Jun-10 9:08am

Thanks,I have already changed the coords,this is the code:
glReadPixels(point.x, iViewPort[3]-point.y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &fdepth);