Fastest methods of determination object's screen size

OpenGL OpenGL: Advanced Coding
1

Hi!

I’m using 8 points of object’s aa bbox and
project them on screen. Min/max of 2d projected screen points are size of object on screen. Problem just one. Speed. I have many objects. Did you know any faster methods of determination object’s screen size? For example may-be use object’s bounding sphere ? How to use object’s bounding sphere to determination object’s screen size ?

Thanks.

2

http://www.gamasutra.com/features/20021011/lengyel_06.htm discusses how to calculate the screen-space bounding rect of a sphere.

If you don’t really need a bounding rect or a pixel count (e.g. if you just need it for LOD control), some cheap approximation based on distance and bsphere radius should do just as well.

– Tom

3

Hi,

I know there is a document referenced in some of the recent NVidia’s stencil shadows paper (or presentation) (by cass, MJK & al.) which is ::

“Jim Blinn’s Corner: Calculating Screen Coverage” in “Notation, Notation, Notation”, and also May '96 issue of IEEE CG&A

I never had a chance to find it online though, so I don’t know if the method is worth or not…

does anyone has a link to a free electronic version of this article ? cass ?

Nicolas.