I use StumbleUpon and ran into this tonight: Crazy Weird Lazer
How does it work?
I’d guess it’s a computer program and that there is some sort of receiver that gets a reflection of the laser and can tell how bright it is and adjusts the movement accordingly…?
Are you sure it’s actually a laser? Could just be an animation. Still impressive.
Looks real to me. Like OpalCat said, it’s just a lazer paired with a camera, running according to some program (or set of programs, depending on the effect they want to achieve) that detects edges and traces them.
Looks real to me, too. In fact it looks like some kind of demo or even homework assignment for a controls class, adjusting a laser that aims (probably with tiny motorized mirrors) to follow the lines. It reminds me of little robotic cars that trace lines drawn on paper.
By the way, this may well not use any camera (other than whatever filmed it). They may steer the beam one way or the other to keep part of the dot on white paper and part of it on black ink. The brightness of the reflected light would be enough to tell the control system how to move.
[edit] I see OpalCat already said this - sorry I didn’t notice before!
It might be even simpler than that. Laser shows use piezoelectrically-driven mirrors to draw shapes. What if the laser was bouncing off such a mirror system and they simply directed it onto a piece of paper, then drew the path it traced (in the shape of a heart) with a magic marker?
No feedback mechanism needed. It’s like drawing a bullseye after you’ve shot the bullet through a target.
Did you watch the whole video, or only the first part with the heart?
Ah – only watched the first part – it seemed to go on interminably, so I simply bailed after the first half.
The puzzle could’ve been done in the same ay, but it seems a lot less likely. Followers aren’t hard to do – I was just noting that the heart could’ve been done a lot easier than the posts suggested.
Oh, the cat would love that… 
I want one.
I’ve seen things like this at shopping malls. Light images are projected onto the floor of a children’s play area, and the kids chase after and otherwise interact with the pictures, which move according to the kids’ motions.
Hijacking the thread: The neighbors came home with a red beacon similar to the one Starsky and Hutch slapped on top of the Torino back in the day, except that this one plugs into a 110 outlet. They found it in a yard sale for 50 cents.
One of the knucklehead labs is fascinated by it. She stares at it, follows the red light around and around on the floor, walks away and is drawn back. The other one (the older of the two) couldn’t care less.
We now return you to your regularly scheduled discussion.