When buying projector, settings for mapping (2D, 3D)

[philwues]

Does every projector support the fact were it only projects lights in the places were needed?

So you don't have places outside were it would shine "black"

For instance, if plasma tv's project black, it's just OFF and normally when LCD tv's would do this, they would still have a led burning an almost "black" color.

And what is this setting on you projector??
+ how do you do 3D mapping?

I don't have a projector yet and sorry for the grammar.

[GeeEs]

I guess it will always "shine black" around a mapped object. You can't just turn off some pixels in a projector . However, it is possible to make a hardware mask with contours of mapped object(s) of some sort of cardboard/opaque plastic sheet/foil and place it in front of the projectorlens (watch out for to much reflections when using foil). This will eliminate most of the direct "black shine". It won't let you create sharp edges, while the hardwaremask won't be in focus.

The best way imho is to use a little ambient light that washes out the surrounding "black shine" but is ambient enough to not disturb the projected/mapped objects.
I guess a DLP projector will have some advantages here while they usualy have a better contrast compared to LCD projectors.