Create water surface using particles

(bouncing) - In the last video, we saw this preview of a shot from Finding Nemo where we've drawn the particles as balls to illustrate their motion. For the final shot, we used the particle positions to compute a surface. Then we rendered that surface to look more like water. To draw a smooth surface using individual particles, we use an analogy involving heat. First, imagine these particles are little heaters. Next, pretend we have a thermometer which tells us the temperature at any point in space. For example, the particles might be exactly 1,000 degrees, and as we move away, things cooled down. Let's say this point over here is exactly 100 degrees, and there isn't just one point in space which is 100 degrees, but many points. So if we connect all points where the thermometer says 100 degrees, we get a curve shown here in yellow. And that's the trick. Now we can fill in this yellow curve with a solid blue color to give us something that looks more like a puddle of water. If the particles are far apart, they each form their own isolated region, like a droplet. As they get closer, the droplets start to glob together, mimicking real water. Here's a version with a few more particles. This is starting to look like water. It would really look like water if we had a few thousand particles. For use in our movies, we work in three dimensions, and the curve becomes a surface like in this shot from Finding Dory, or in this more extreme water simulation also from Finding Dory. Here's an example from Monsters University. Here we're simulating paint, instead of water. We've turned up the viscosity since paint is more viscous than water. We weren't exactly sure how paint would behave so one of the first things we did to create this shot is to videotape reference of real paint. The reference really helped us create a believable look. Let's pause here so you can practice using the next exercise. Good luck. (playful music)