I am working on a sci-fi project, and we want to obtain a certain effect.
Having a character levitate some kind of hologram above a desk, hologram in the shape of a box, like a cubic screen.
And inside this cubic hologram display, zooming on certains parts of a 3D model.
while the cubic hologram remain at the same size on the desk.
The thing is, the concept seems like basics sci-fi stuff, but we have absolutely no idea how to obtain this effect in 3D.
We thought of Bolean meshes, but the bolean way of "cutting" objects is not dynamic.
Or to fake the effect using a DepthofField map, but it would only help us haide background object, and not frontground.
The ideal would be to have a "render box", a box in the scene where everything inside is rendered, and everything outside is not.
The hard part is also to have the meshes "sliced" and not just hide and unhide.
Would by any chance any of you know a way or if it's plainly impossible?
At this point we are using Maya and Octane Render, but we're open to switch to any software or render that would make it work.
I got some succesfull attempt with using the "cut face tool", and parenting their gyzmo to locators on the side of the "renderbox", but I still have issue with animated objects.
the "cut" act as if the animated object was still at the same spot as he was at frame 1
Despite the fact that he had moved.
The boolean operation in Maya is Dynamic, as is nearly every operation, due to how the history chain works.
Create your Boolean using the bounding box, then move the booleaned object using the history transform object that's left in your Outliner. It should have the same name as your booleaned object, but with an icon that looks like a sheet of paper with a red arrow on it.
If this solution isn't good enough for you though, there is the Puppet CSG shader, though it's for Mentalray, not Octane.
Easiest least efficient option: Dynamic booleans.
Scripted options supposing you can get someone to code this simple shit:
Clipping: A trivial approach will however make your mesh look hollow and badly lit in its insides.
Another approach is to basically for all points past a certain axial w to project them flatly on a plane, repeat for all sides of the cube. This approach will net anything outside the cube "flat" on those areas, avoiding some other problems but also looking bad.
Another approach would be to do the previous approach, but keep track of the parts that got flattened, then make them of another color in compositing or even post.
OP here, an easy way has been found!
make the "renderbox" a speular material, with full refraction.
then, make the other object movable proxies (or object tag for C4D users), then make them camera invisible.
They will still appear in teh refraction of the box!
You need to check out shadow only or like matte materials. In 3dsmax there's a material that lets you "chop" an object out of a scene. So you'd render in a few different passes:
1) render the normal scene, with the characters, and no box.
2) render a pass with just the box itself, chopping a hole in the frame.
3) render just the elements that are supposed to be inside the box, by themselves.
4) in your composite program, pass 1 goes in the back, then the elements inside the box, then the layer with the hole cut in it on the top.
5) if you want to add some special effects to the box/area, render a pass of just the box itself as a matte black object, and anything else that passes in front of it as a matte/chop out object. Comp that layer over top of the whole thing, and apply effects like color correction/opacity/glow/etc.