RE: [Flightgear-devel] Screen to cartesian co-ords?
On Friday, 5 November 2004 15:16, Aaron Wilson wrote: > Paul, > You may want to look into the gluUnProject(...) function. > Aaron Thanks Aaron. I have it all working nicely with glReadPixels and gluUnProject. Not sure exactly how the Z cursor component is determined but it seems to work just fine and the resulting lat and lon values look correct. I think I'll just leave the blackbox alone and get back to writing the taxiway code. Paul ___ALL-NEW Yahoo! Messenger - all new features - even more fun! http://uk.messenger.yahoo.com ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Screen to cartesian co-ords?
Paul, You may want to look into the gluUnProject(...) function. Aaron At 04:29 PM 11/4/2004, you wrote: Thanks, that makes a lot more sense to me now. I'll see what I can glean from the PPE code. On Thursday, 4 November 2004 23:06, Norman Vine wrote: > RE: [Flightgear-devel] Screen to cartesian co-ords? > If you have enabled DepthBuffer operations in OpenGL > the rasterizing process keeps track of the depth component > of each pixel in the ZBuffer. > > Note this won't work to well with wireframe and that the > Z component is the distance from the eyepoint > > = > > For an example that does this using SSG > > PPE keeps track of the position for a 3d Cursor > > $PPE_SRC / src / viewer / ppeViewerDraw.cxx / ppeViewer::update_3D_cursor() > > Note I am quite swamped with work and won't have time > to explain the PPE code but you have the source :-) > > http://prettypoly.sourceforge.net/ > > Norman ___ALL-NEW Yahoo! Messenger - all new features - even more fun! http://uk.messenger.yahoo.com ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Screen to cartesian co-ords?
Thanks, that makes a lot more sense to me now. I'll see what I can glean from the PPE code. On Thursday, 4 November 2004 23:06, Norman Vine wrote: > RE: [Flightgear-devel] Screen to cartesian co-ords? > If you have enabled DepthBuffer operations in OpenGL > the rasterizing process keeps track of the depth component > of each pixel in the ZBuffer. > > Note this won't work to well with wireframe and that the > Z component is the distance from the eyepoint > > = > > For an example that does this using SSG > > PPE keeps track of the position for a 3d Cursor > > $PPE_SRC / src / viewer / ppeViewerDraw.cxx / ppeViewer::update_3D_cursor() > > Note I am quite swamped with work and won't have time > to explain the PPE code but you have the source :-) > > http://prettypoly.sourceforge.net/ > > Norman ___ALL-NEW Yahoo! Messenger - all new features - even more fun! http://uk.messenger.yahoo.com ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Screen to cartesian co-ords?
Paul Surgeon writes: > > On Thursday, 4 November 2004 22:02, Aaron Wilson > wrote: > > Paul, > > NeHe has a good example of how to convert > the screen coordinates > > into OpenGL coordinates. > > > http://nehe.gamedev.net/data/articles/article.asp?article=13 > > > > Aaron > > I found that article very helpful. > > The part I don't understand is how the glReadPixels > get's the winZ co-ordinate. > I mean I'm looking at a wireframe ellipsoid from an > odd angle - how does it know how to return the Z > co-ordinate of the surface of the ellisoid? > Surely I have to tell it where the surface is so that > it knows how to intercept the surface and not try to > pick a point into infinity (in front of and behind my > cursor)? > > That is what is not explained anywhere I look. If you have enabled DepthBuffer operations in OpenGL the rasterizing process keeps track of the depth component of each pixel in the ZBuffer. Note this won't work to well with wireframe and that the Z component is the distance from the eyepoint = For an example that does this using SSG PPE keeps track of the position for a 3d Cursor $PPE_SRC / src / viewer / ppeViewerDraw.cxx / ppeViewer::update_3D_cursor() Note I am quite swamped with work and won't have time to explain the PPE code but you have the source :-) http://prettypoly.sourceforge.net/ Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Screen to cartesian co-ords?
On Thursday, 4 November 2004 22:02, Aaron Wilson wrote: > Paul, > NeHe has a good example of how to convert the screen coordinates > into OpenGL coordinates. > http://nehe.gamedev.net/data/articles/article.asp?article=13 > > Aaron I found that article very helpful. The part I don't understand is how the glReadPixels get's the winZ co-ordinate. I mean I'm looking at a wireframe ellipsoid from an odd angle - how does it know how to return the Z co-ordinate of the surface of the ellisoid? Surely I have to tell it where the surface is so that it knows how to intercept the surface and not try to pick a point into infinity (in front of and behind my cursor)? That is what is not explained anywhere I look. Paul ___ALL-NEW Yahoo! Messenger - all new features - even more fun! http://uk.messenger.yahoo.com ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Screen to cartesian co-ords?
Paul, NeHe has a good example of how to convert the screen coordinates into OpenGL coordinates. http://nehe.gamedev.net/data/articles/article.asp?article=13 Aaron At 01:13 PM 11/4/2004, you wrote: I've built a WGS84 model of the world using SimGear routines and need some way of being able to click and draw on the surface of the ellipsoid. Does anyone know an "easy" way to transform a screen co-ordinate into an OpenGL cartesian co-ordinate? (Which I can then convert to polar co-ordinates) Thanks Paul ___ALL-NEW Yahoo! Messenger - all new features - even more fun! http://uk.messenger.yahoo.com ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
