Re: [Algorithms] Re : R: Sphere to rectangle
Brought to you by:
vexxed72
Menu
▾
▴
Re: [Algorithms] Re : R: Sphere to rectangle
|
From: Diogo de A. <dio...@ne...> - 2010-01-08 15:50:46
|
Hi Benjamin, Your solution almost works for me… It works when the camera is head on to the center of the sphere: <http://www.spellcasterstudios.com/sphere_rect_problem01.jpg> http://www.spellcasterstudios.com/sphere_rect_problem01.jpg But when I turn left or right, I get: <http://www.spellcasterstudios.com/sphere_rect_problem02.jpg> http://www.spellcasterstudios.com/sphere_rect_problem02.jpg <http://www.spellcasterstudios.com/sphere_rect_problem03.jpg> http://www.spellcasterstudios.com/sphere_rect_problem03.jpg This might be related to the projection part, I’ll look into it… What do you mean by: “Up and right vectors based on the camera and light positions (and the camera Up).”? I’m just accounting for camera orientation to calculate the up and right vectors… Are you suggesting something like: View=LightPos-CameraPos Right=cross(CameraUp,View) Up=cross(View,Right) ? >From the more practical standpoint, from what I understand, you’re applying a scale factor to the radius to account for distance… How did you came about this formula? You didn’t happen to need something similar for spotlights/cones? Thanks, Diogo From: Benjamin Rouveyrol [mailto:pth...@ya...] Sent: sexta-feira, 8 de Janeiro de 2010 15:03 To: Game Development Algorithms; dri...@li... Subject: [Algorithms] Re : R: Sphere to rectangle 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 |
