View Full Version : Picking Troubles with Selection!!

04-22-2001, 03:43 AM
Hello friends,

Please help solve this problem...

I am trying to pick some "GL_POINTS"...
They get picked fine... unless i Rotate...
as soon as i rotate they won't anymore be picked(i get get 0 hits).... if i rotate about one of the points then only that one gets picked(maybe because it essentialy is in the same position even after rotation?)

I can't understand why this is happening...
I have the redbook open in my lap right now... and the code i used for picking is right out of it (Example 13-6, pickdepth.c, pg 547)
The example contains no transformation though... I can't for the life of me understand why transformation on the model_view matrix have any effect on my picking as, picking's got to do with the projection matrix...

And does anyone know about an example on how to use the back buffer for picking?

Thanks for your time...

Tim Stirling
04-22-2001, 06:52 AM
When you draw the scene for the selection make sure you are apply the same transformations (rotations etc.) as for the normal rendering, this can also be achieved by saving the modelview matrix and reloading it.

04-23-2001, 03:36 AM
Your a life saver Tim!! Thank You!
It works fine now http://www.opengl.org/discussion_boards/ubb/smile.gif)