If you really want to do it manually, you'll need to learn some maths. You need to calculate the distance of a point on a sphere from the camera (the camera position in QC is (0,0,-1) if I remember right) to determine size and perspective transform.
I don't understand why you need to convert though - if you have the xyz position, why not just tell QC to draw your image at that xyz position? You could also use the 3D transform patch perhaps? Chris 2009/11/3 Sune Watts <[email protected]>: > Sorry if I was unclear: > > How to translate an (x, y, z) point into (x, y) screen coordinates -- > > For example, you have a rotating globe and want to know the screen > coordinates of a certain city on the globe. > > > Best regards > Sune Watts > > > --- > > > On Tue, Nov 3, 2009 at 11:02 AM, Chris Wood <[email protected]> wrote: >> >> QC supports 3D space already. There's 2 ways to show a 2D image: >> Billboard (this is best for overlays and the like, and is 2D based) >> and Sprite (this is similar to billboard, but exists in full 3D space >> so you can move it on Z, and rotate on all 3 axis. >> >> Most likely, sprite will cover your needs. >> >> Chris >> >> >> 2009/11/3 Sune Watts <[email protected]>: >> > Hello all; >> > >> > I need to pin a 2D billboard onto a (moving) point in 3D space. >> > >> > I haven't been able to find any info on the z-axis scaling QC employs. >> > >> > Has anybody got a handle on mathematically converting a point in 3D >> > space to >> > 2D screen space? >> > >> > >> > All the best >> > -SW >> > >> > _______________________________________________ >> > Do not post admin requests to the list. They will be ignored. >> > Quartzcomposer-dev mailing list >> > ([email protected]) >> > Help/Unsubscribe/Update your Subscription: >> > >> > http://lists.apple.com/mailman/options/quartzcomposer-dev/psonice%40gmail.com >> > >> > This email sent to [email protected] >> > > > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Quartzcomposer-dev mailing list ([email protected]) > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/quartzcomposer-dev/psonice%40gmail.com > > This email sent to [email protected] > _______________________________________________ Do not post admin requests to the list. They will be ignored. Quartzcomposer-dev mailing list ([email protected]) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/quartzcomposer-dev/archive%40mail-archive.com This email sent to [email protected]
