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## Building crowds

Current time:0:00Total duration:1:53

# 1. Counting with tables

## Video transcript

- Hi, I'm Fran Kalal. I'm a cloth and sim technical director at Pixar Animation Studios. That means I get to take what
I know about art and design and make outfits, and what I know about math and physics to make them move. I'm here today to talk to you about crowds like the large one behind me. Except that the one behind me is physical, and the ones we need to make for our films are virtual. That means they exist
only on the computer. We saw in the last video
how lots of robots were made using only a few parts through the use of combinatorics. So follow me to learn more about what combinatorics is and
how we use it at Pixar. To understand how many robots we can make from a bin of parts, let's
start with an example where a robot has one head and one body. And I've got two different
heads to choose from and three different bodies. So I can take this head with this body, or this same head with this body, and that's already two different robots. And clearly I can make a whole lot more. A great way to keep track
of this is with a table where I'm going to place
the heads along the columns and the bodies along the rows. This cell means put
this head on this body. There are six cells on the table, so there are six different robots even though we only have
five different parts. This is a great example of the fact that finding a good way
to think about a problem makes it easier to solve. How many robots could you make if there were different
numbers of heads and bodies? You can explore that question
in the next exercise.