Interacting with shadows

[Stremik]

I've just came back from "Children's Museum" where I took my kid on his birthday

(Holy Mother of God! He's 10 allready!), and there I saw the coolest thing.

There is this projector and the white screen. Projector continuously

shows one thing. A stream of small, colorfull pieces of glass pouring

from top, down. The cool thing happens when you stick your hand

in to the lightbeam coming from the projector. As soon as the shadow

of your hand uppears on the screen, it acts as a collision object and

pieces of glass start piling up on your hand.

There is also another progector which shows a sworm of butterflies

flying in a random pattern.

The moment your shadow uppears on the screen, butterflies start

landing on it. Only if you stay put though! If you move a little, you

scare them off and they fly away.

When I saw this, all I could say is :notworthy:

How the heck did they do it?!

Anybody got any ideas?

I also thought that this probably could be recreated in Houdini.

Too bad I don't have enough skill

Vladimir

BTW. Simulation of a projector in Houdini. Does this sound like

a crazy idea?

[exel]

I saw something like this at SIGGRAPH several years ago, maybe in 2000? Projected letters of text falling down a white screen, anyone remember that?

Sure, I reckon you could pull something like that off in Houdini without too much trouble... Sounds like a good idea for a Houdini Challenge here!

[Visual Cortex Lab]

I saw something like that at the Sony store in SanFrancisco.. on the floor there were like a white screen/pool where from the ceiling was projected various stuffs.. including some metaballs which reacts to your feets position..

that was awesome cause kids were playing with it like it was a regular toy... and me (and my collegues, all over 30 years old ehehe) were playing like it was a damn cool kid toy for us, the "real kids" in that case

cheers

[michael]

perhaps as a variation on this:

http://odforce.net/forum/index.php?showtopic=26

[Mcronin]

I've seen this same exhibit. I think it's actually just image analysis. You put your hand infront of the light, which casts a shadow, a camera shoots video, analyzes the frames as they come in and, determines a ccollision shape for the falling particles. I think it's something not that difficult to do especially since they are doing it in 2D.

There was a link someone sent out at work here a while back about a guy working with this same type of simple shape analysis. He has a box on his front door his cat can use to go in and out. The box has a locking mechanism. When anything tries to come in throught the box, a camera shoots a snapshot and compares the image to a database of snapshots to determine if it is his cat trying to get in, and whether the cat was carrying anything (dead mouse, bird, whatever). If the comparison is good (it is the cat and it's not carrying any dead animals) the door would unluck and let the cat in. All in all I think the link said it took fractions of a second to snap the picture and analyse it.

So maybe this could be a challenge (probably and easy one) make a simple image or animated image sequence, a black and white image sequence, apply it to a grid, creep particles onto the grid, and have them collide with the black part of the image. I'm pretty sure they did something similar to this in FotR with that Squid creature in front of the mountain entrance, to drive water droplets on it's skin.