[Algorithms] Re : R: Sphere to rectangle
Brought to you by:
vexxed72
Menu
▾
▴
[Algorithms] Re : R: Sphere to rectangle
|
From: Benjamin R. <pth...@ya...> - 2010-01-08 15:29:36
|
Hi, The way I solved this (but a bit math heavy): If R is the light Radius and D the distance between the camera and the light: NewR = D * tan(asin(R/D)) Then you compute Up and right vectors based on the camera and light positions (and the camera Up). You end up with 4 corners: LightCenter +|- Up * NewR +|- Right * NewR You can project them and this should give you your bounding rectangle. If someone has a simpler solution, I'd be most interested ^_^ Ben ________________________________ De : Diogo de Andrade <dio...@ne...> À : dri...@li...; Game Development Algorithms <gda...@li...> Envoyé le : Ven 8 Janvier 2010, 9 h 28 min 54 s Objet : Re: [Algorithms] R: Sphere to rectangle Hi! That's basically what I'm trying to do with the "wrong" solution, although I don't tell it like that... It was a good thought... I had to think about it for 2 mins before I understood that was exactly what I was trying to do... Visually, you can see the problem at http://www.spellcasterstudios.com/sphere_problem.jpg With your solution (and my initial one), I'd get the red points (and their projection, the yellow line), which is smaller than the correct solution (the purple points/projection), which has the correct size... Thanks! Diogo -----Original Message----- From: dri...@li... [mailto:dri...@li...] Sent: sexta-feira, 8 de Janeiro de 2010 13:54 To: gda...@li... Subject: [Algorithms] R: Sphere to rectangle ----Messaggio originale---- Da: dio...@ne... Data: 08/01/2010 13.45 > Hi all… > > I’ve been wrestling with a problem for some days now, and I > honestly can’t seem to figure an elegant solution… > > I want to find the rectangle that bounds a omni light source, > so the problem is: given a sphere with center C=(x0,y0,z0) and radius RADIUS, what is the bounding rectangle rect=(rx1,ry1,rx2,ry2) on screen? Ok, I read this ML only for educational purpose, so...well, I'm sure I will suggest the wrong solution :-D Arent'you simply trying to do screen-aligned billboarding? I mean...the bounding rectangle around a sphere of a given radius, on screen...is not always the same rectangle simply billboarded? ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ GDAlgorithms-list mailing list GDA...@li... https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list Archives: http://sourceforge.net/mailarchive/forum.php?forum_name=gdalgorithms-list ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ GDAlgorithms-list mailing list GDA...@li... https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list Archives: http://sourceforge.net/mailarchive/forum.php?forum_name=gdalgorithms-list |
