Liquid wall effect--is there a better way?

[Barry_S]

I'm about to shoot a music video (with the help of some DVXUsers ;D) and I'm planning on having a special effect where the singer places her hand flat on a wall and a circular section of the wall ripples like water. My plan is to first take a shot of the wall without the talent to use as a background plate. Then, we'll attach a circular green screen to a section of the wall and shoot the talent placing her hand against the green screen section. In post, I'll key out the green screen and and composite it with the background plate. The ripple effect will be done on the background plate. The final effect will be spreading circular ripples on the wall underneath the talent's hand.

I'm about to run some tests, but does anyone have any suggestions for better ways to do the effect? I'm a little concerned about shadows when the talent touches the green screen and having to rotoscope the matte frame by frame (ugh!). Thanks.

[glassblowerscat]

Difference Key? Although the only time I tried it, it didn't work that well, it was mostly (looking back) because I had not taken proper care in lighting the scene.

A difference key would keep the shadow.

[Barry_S]

Excellent suggestion and worth trying. Thanks.

[Curugon]

Be sure to do some takes where you swap the green screen for a mirror. So for the 3D effect you can texture the wall with a bit of reflective surfacing, using the mirror plate. It'll add a nice realistic touch.

[Barry_S]

Curugon--thanks, that's an awesome idea. *I can buy a few sheets of reflective mylar and composite in a bit of the reflection over the background plate.

[Curugon]

Good luck, Barry! Post results if you can.

Oh, and if you do the reflection pass, be sure to composite it with a subtle displacement map for a rippling effect.

[J.R. Hudson]

Is it out of the question to go OLD SCHOOL and use actual water (carefully placed and lighted of course) ?

[Barry_S]

Ok, a displacement map. *Every suggestion adds a few more hours to postproduction *::). *I'll definitely post the final result. *I ran some tests to day and I clearly have some work to do with shadows over the green screen.

John--I want the wall to look like liquid. *I suppose I could shoot some real water and throw a stone in to ripple it. *But it would still have to be nicely composited. *Something to try maybe. *Anyway the shoot is Frioday and Saturday, so my work in post will be cut out for me--that's for sure.

[theos]

lets see the grabs barry!

[Beat Takeshi]

Hi Barry, i would use a green wall with marks at each corner of the frame and create the wall in 3D. I would shoot the actual wall you are thinking of straight on and the angle you plan and use that for a texture. Make the wall a high poly count so you can ripple the geometry without noticable polygons. This way you can just ripple the wall instead of everything thats in the scene and maybe make dust fall or something giving it nice detail.
Another thing about doing it in 3D is that you can mimic the lighting and cast shadows with dummy objects for the hand and arm. The 3D effect will be at the right angle too, as far as i know, you have to apply the effect on a layer, turn it into a 3D layer and try to line it up with your wall to get the effect. Another thing is that the effect in AE is applied to the whole layer giving you rippled edges that you have to get rid of with masks.

[Barry_S]

Thanks, Opressor, another good suggestion, but I don't know, the solutions seem to be getting more and more complicated :). I haven't done any 3D work for awhile, so it would mean coming up to speed on yet another application and another level of complexity. The control would be greater--you could do anything to the wall, but the workflow would really slow me down. I've completed my first plate and green screen shots and would love to stay in Vegas, but an AE solution would still be simpler than a 3D app (for me). Unless you're volunteering to help--that is ;D.

[Rich Lee]

you could do this in after effects using 3d layers..maybe?

[dust'n the callipygous]

i'm looking to do a similar effect but on a smaller scale with just a mirror on a wall. i'm thinking no special effects and simply shooting one angle of someone reaching towards the mirror. we'd then take the mirror's frame and place it around a large bucket of water with a replica wall behind it. i'd just take a different close-up angle with the whole contraption lying on the ground and hope gravity doesn't affect the person's hair too much. would this be easier to just do in post? i've got FCP just got ahold of motion, but i'm not familiar with it, yet.

[oneinfiniteloop]

If you film a bucket of water rippling from above then used that to drive a displacement map that would work.

[kai]

Below is a quick n' dirty after effects file that might get you started. In it are different comps. "wave displace" is just that. "Wall" is where it's applied, and "composite" is where you'd build it into your shot along with your other plates. It uses wave world and displacements.

Keep in mind this isn't pretty (at all) and will require further tweaking to apply it to your shot. It's just a starting point for a possible technique, so it will probably need to change completely depending on how your shot is actually lensed. I just didn't have more than a minute or two.

Hope it helps a bit...

Preview movie (18MB): http://www.kylestauffer.com/dvx/wall.mov
After Effects file (800k): http://www.kylestauffer.com/dvx/wall.zip

[mcshyd]

barry, I think you're first idea is great, and is all you need to complete the effect. I definitley think that 3d is not needed at all, and would probably look way worse (at your skill level). I only have two sugestions, and they both exist in the production phase- make the circular green screen bigger than you thought you needed, cause you can always pull in the mask later, and place one light abve and one light below the screen, directly on the wall. this will kill your potential shadow problem. Also if youre having probs wth the screen (im in the middle of a huge greenscreen project shot with the dvx, which is hell), I've had amazing results with an ae plugin made by the dv garage people out here in san francisco (pixel corps, alex lindsay). It's doing amazingly well on dvx footage, which just freaking sucks for green screen. can't wait to see it.