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Balu
11-09-2003, 10:56 PM
Hi, I have drawn some images on the screen by using TextureMapping. In the OnSize(...) event i set the projection and viewport like this:

glViewport(0, 0, cx, cy);
gluPerspective(0.0f, fAspect, 0.0f, 1000.0f);

At the time of displaying the images i set the projection as

glOrtho(anViewport[0], anViewport[2], anViewport[3], anViewport[1], -1.0f, 1.0f);

The problem is , Just I moves the image to the end of the viewport. After that I can access the Feed back buffer; The Feedback buffer won't fill with the proper info. But when i place the image within the viewport area the values in the Feedback buffer are properly filled. How to get the proper values when the image is outside the viewport.


[This message has been edited by Balu (edited 11-09-2003).]

Bob
11-10-2003, 02:20 AM
The feedback buffer will return whatever gets drawn. Items outside the viewport will not be drawn, and will therefore not end up in the feedback buffer. Clipped items will be put into the feedback buffer after they have been clipped, meaning, say, a triangle that intersects the viewport edge can generate two or more triangles into the feedback buffer.

And your call to gluPerspective is not correct. The near plane value must be positive.