Vfx scenario, 3d camera dolly in on a keyed person. No zooming.

[Joel Arvidsson]

Im curios if there is a simple way to have a keyed person, on a 2d plane in a 3d space, sitting on a stair step, and push in towards this person in post with a 3d camera in post instead off for real.

The problem with this scenario is that the person will have two points of contact with its surrounding. One point for the butt on the stair step, but also one for the feels on the ground. And these two contact points would have little to much different zdepth to not create problems. For example if you set the 2d plane (with the keyed person on) to on the stair step youre feets would be sliding on the ground. You could get away with a less detailed ground since it would be much more forgiving or you could switch the dolly for a zoom but that no fun=)

Sure could switch the dolly for a zoom but that no fun=) , or you could do the camera push in physically while shooting the green screen plate.
But sometimes its not practical. Maby you want to do a really long dolly in wich your studio space might not allow or you like to ad serval passes with the same person (and dont have a motion control).

Im just curios if there is a way I missed. It could be useful at times. I would guess you could bend the 2d plane to imitate the legs sticking out in z depth and than projekt on to that to get less warping.

 

[Marcus Friedlander]

Hey so I’m not a vfx expert in any way but a thought popped into my head while I was reading your post.

To solve your 2D plane problem, can you set the plane on the persons butt, track it, and then set a separate 2D plane for the feet that then gets combined and tracked together? I don’t know if that’s something that’s possible to do, but if it’s is, then you could just do your 3D push on top of your combined 2D plane right?

 

[paulcurtis]

Im curios if there is a simple way to have a keyed person, on a 2d plane in a 3d space, sitting on a stair step, and push in towards this person in post with a 3d camera in post instead off for real.

Like most vfx stuff it's shot dependent - what's the focal length and distances of the 3D move for example.

I have done things like this before - taking a 2D shot and them adding a move afterwards. In your particular case i would consider roto'ing the front of the legs as a separate plane so it can be moved slightly forward in depth to create a degree of parallax. I've cut plenty of limbs out before to achieve something like that and actually so long as there is parallax the brain can be quite forgiving IMHO. The brain *expects* it to be a real move and isn't looking for problems.

Having said that you'd be surprised that perhaps not even doing that would work.

Another approach is on that 2D plane if you have some displacement or normal mapping you can push that part of the plane out in depth to also do the same kind of thing (this approach is software dependent though). This would work very well. This works great on skies with clouds!

cheers
Paul