Beginning Projection Mapping

[baustellen]

Originally Posted by PCProject

Pretty much yes. Focal length of the lens in C4D needs to be same as the final projection one.

Ah, the focal length as the projector has? But the focal length is adjustable at the projector, so should I use the min. or max. one?
Do I also need to take the focal lense of the Camera, which I took the photo with into consideration?

[baustellen]

Originally Posted by deepvisual

well cameras chips are fixed at the centre of the lens. projector chips are intentionally fixed off centre. this allows the projector to be positioned either at the top of the bottom of the screen.
so optically, to imitate a projector that has a real world position opposite the bottom of a screen, you have to position your camera opposite the centre of the screen.

I get what your point , but "opposite the centre of the screen", I don't get where that should be. Could you maybe make a draft, to make it more understantable?

[vjneef]

here is a picture
and explanation

http://en.wikipedia.org/wiki/Perspective_control_lens

wouldn't it be better when starting mapping to start without any software
to get some understanding of what happens in the projection/perspective ?

[deepvisual]

here's why I am not a painter...


the projector is designed to be positioned at the bottom of the screen

[baustellen]

Man, you are the master of desaster. That was exactly where I was stucked. Appearantly it doesn't matter if the real projector is positioned at the bottom or the top of the screen, in both cases the virtual Camera has to be in the middle of the screen, right?
And another one: In case not the whole range of the possible projection-image is used. E.g. I use only the top 2/3, do I have to position now the virtual camera in the middel of the 2/3 or in the middle of the whole screen. I would say in the middle of the whole possible screen, right?
Anyway, thanks a lot!!! If you are ever in Israel, I will invite you to some beer.