How to Clip an object moving through an invisible wall

[detbear]

I'm moving an object towards the camera through a waterfall.

 

I want it to emerge through the waterfall.

 

What I've been doing is using a green wall that I key out later. This leaves just the object as it passes through.

 

Is there another/ better way to "Clip" an object in A:M so that I can bi-pass the green screen wall???

 

William

[Rodney]

There are two primary approaches that I can think of:

 

1) Bypass the need for clipping entirely by compositing the whole shot in A:M

 

2) Use Boolean cutter(s) to clip the object

 

Both methods have their strengths and weaknesses. The first one being that you might not be able to composite in A:M (we would have to know more about your specific situation). For boolean cutters the objects should be 'water-tight' so that individual patches aren't inadvertently clipped by the camera angle.

 

Other approaches that might work: hiding the back part of the object or using material effectors to clip through the object. For accuracy's sake I'd likely prefer the latter.

 

Edit: Attached is a test of the material effector approach.

Note that everything that is black is (or could be) an alpha channel.

I used a bare bones material (only setting was 100% transparency and the effector was set to be a box.

Combining materials with varying levels of transparency might give a nice effect... and setting some internal thickness to the object would help as well.

mat effector.mov

[robcat2075]

Yup. Boolean cutter or Material Effector would be my first gambits.

[detbear]

Thanks guys,

 

I haven't worked with material effectors before. That may take a bit of a learning curve. Maybe the boolean method would be a bit easier.

 

Cheers,

 

William

[Rodney]

Maybe the boolean method would be a bit easier.

 

Both setups take almost exactly the same time although with Material Effects you have more options (so exploring those might take more time)

As mentioned, assuming your model is not all of one unibody mesh entirely enclosed by splines you might have some problems with stray artifacts with boolean cutters.

 

In many ways they are the same thing.... in fact I wouldn't be surprised to discover that underneath it all they are the same thing with different approaches in the UI.

 

The benefit of Boolean Cutters might be the nesting of bones/booleans.

I'm not sure how that might be accomplished with Material Effectors outside of using them as Action Objects.

 

If your object is not a closed mesh I believe I'd opt for the Material Effect.

[Rodney]

William,

I should have thought to say that your method of a moving mask/wall may be just as useful as these other techniques.

Assuming you have access to After Effects or other automasking program that might in fact be the best approach.

I wouldn't want to remove each mask individually so the other techniques would work in those cases that require more manual labor.

 

A benefit of using the moving wall would be that you could layer in additional effects as well.

For instance, if you kept your wall a solid color you could add particle effects with that color as well.

Then when you remove that mask the remainder of the imagery would show through.

 

I always hesitate to recommend creating a mask when it is unnecessary (i.e. if the background can just be removed via an alpha channel) but there are certainly times when creating the mask will work well.

 

Example attached: (note that I colored the wall black in the first pass to demonstrate the particle masking).

 

 

Layering in effect.mov

[Rodney]

It's not every day we get to recommend multiplane effects (and much of that is taken for granted) but if the project calls for it you could try an all A:M approach where you would replace your green walls with multiple walls of varying transparency with the desired imagery on it. Then your character or object would appear to emerge from that 'real' space created within the walls.

[Rodney]

Here's a slightly modified version from a camera view.

In order to be remotely useful I'd say a second transparency map would need to be added to account for more depth and the water splashing off the character and the rock.

Converting the walls to a box and filling that box with animated material to simulate the waterfall might produce a more volumetric effect in this specific case.

[John Bigboote]

Great test, Rodney! I would definitely combine any effect you do with a particle/sprite effect with collision-detection to get some interaction with the water and the character. If you are sold on the green-screen method, you could use multiple layers of green... the 1st at 15% opacity, then maybe 45%... and the final 100%- so you will get more of a gradual emergence.

[robcat2075]

one advantage of the material effector approach might be that you could have a fuzzy edge. I'm not sure if that's true but possibly it is.

[detbear]

I will also add that I'm trying to make a very realistic waterfall to move through. BUT more of a waterpark or disney ride version. rather than a foamy, smokey fluffy thing.

 

Yeah...After Effects is a primary part of my pipeline. The Green Screen method works good. But takes a few more steps.

 

I'm working on a trailer for a kickstarter pitch. It is vital that whatever goes in the pitch is Feature quality. A good opportunity for A:M to

display it's abilities. BUT I have no budget on this particular project to hire help.

 

Actually I've done pre-production on this now for over a year and much of my forum inquiries have been directly related to it.

 

RobCat.... I like the material effector "fuzzy edge" potential. Post work can get that in some cases. There are obviously advantages and disadvantages.