Re:Pixar's senior scientist explains how math makes the movi...
by ColinWright on Sunday March 18, 2018 @03:08PM
(#16613651)
That point is actually covered in the article:
Merida's hair is made of 100,000 individual elements. "If you know any combinatorics, you know that if you have n objects, you have n² possible collisions," he says, or 10 billion. How can you render so many collisions quickly enough to be usable? You have to create a new spatial data structure that culls extraneous collisions without being too lossy.
So he's saying that naively with n objects there are n² possible collisions, but they have to do clever things - such as you suggest, or even cleverer - to reduce that. Already there. In the article.
But the GGP's point is that there aren't n² possible collisions, there are only n(n-1)/2 if you allow for the symmetries. But is still grows quadratically, and that's the point being made. Quadratic is too fast.
Merida's hair is made of 100,000 individual elements. "If you know any combinatorics, you know that if you have n objects, you have n² possible collisions," he says, or 10 billion. How can you render so many collisions quickly enough to be usable? You have to create a new spatial data structure that culls extraneous collisions without being too lossy.
So he's saying that naively with n objects there are n² possible collisions, but they have to do clever things - such as you suggest, or even cleverer - to reduce that. Already there. In the article.
But the GGP's point is that there aren't n² possible collisions, there are only n(n-1)/2 if you allow for the symmetries. But is still grows quadratically, and that's the point being made. Quadratic is too fast.