I think it's important to differntiate between "zoom" and "pan forwards/backwards".
Zoom: change the field of view without changing the camera position, for example, when a photographer uses a zoom lens. This is possible in both perspective and orthographic projections. Pan forwards and backwards: Move the eye position closer to or further away from a view point, without changing the field of view. This is well-defined for perspective, but is meaningless in an orthographic projection (and therefore introduces the types of problems that Robert describes below). -Paul -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Robert Osfield Sent: Wednesday, March 19, 2008 3:06 AM To: OpenSceneGraph Users Subject: Re: [osg-users] A question about zooming with orthographicprojection Hi Ke Li, You can do othrographic projection just fine, no need to avoid it. The thing to avoid is zooming into a scene when in orthographic projection - this is something that is just plain broken, you can try tricks with near/far clipping but in the end you'll need to come round the conclusion that its broken and is an inappropriate use of orthographic projection. Is say this from hard experience over the years trying to juggle orthographic and perspective views. Another broken idea that some apps try to do is stereo and orthographic projections of scenes.... It's completely bonkers but some people do it and expect it to work. Use orthographic for what it's good at - external views of scenes, maps, text overlays. Robert. On Tue, Mar 18, 2008 at 6:55 PM, Ke Li <[EMAIL PROTECTED]> wrote: > > Dear all, > > In the following post, Robert said that orthographic projection > should be avoided. > > > http://thread.gmane.org/gmane.comp.graphics.openscenegraph.user/7660/f > ocus=7664 > > But I know that some OpenGL applications do use orthographic > projection with zooming functionality. So I'm a little confused. > > Can any one give me some enlightenment? > > Thanks! > > Ke Li > > ________________________________ > Connect and share in new ways with Windows Live. Get it now! > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph. > org > > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
