PDA

View Full Version : Image plane equation



Spela
11-08-2004, 12:20 AM
I am rendering a simple 3D object (e.g. a cube, vertices only). I need to know what is the z-coordinate value for the points lying on the image plane. OpenGL transforms the projection matrix so that the z-coordinate remains unchanged and is used in the depth buffer. Can I assume that the focal distance/z-coordinate of points lying on image plane after projection is equal to the near clipping plane value?

To sum up, my question is, how do I find out the focal length or equivalently the z-coordinate of points lying on the image plane after projection (using OpenGL projection matrix, that is)?

Thank you.

Spela

plasmonster
11-09-2004, 04:31 AM
Have a peek at this section on transformations:
http://www.parallab.uib.no/SGI_bookshelves/SGI_Developer/books/OpenGL_PG/sgi_html/apf.html

Spela
11-10-2004, 04:49 AM
Hello!

Thanks for the pointer. I found another link which answered lots of questions, I think it is very well written (it has some typos, but it explains nicely how the modelview and projection matrices are generated). I hope it will be of use to someone else as well.

http://www.ics.uci.edu/~majumder/CG/classes/persprojnotes.pdf