The Physics Glitch Everyone Gave Up On… Finally Fixed

The problem with games and often even movie  visual effects is that they are digital,   so they use simplified geometry that’s often not  quite good enough. It is reality, but simplified.    For instance, if you zoom in on real bread  dough, you see small bubbles forming. Uh-oh,   that means you would need to have bubble physics,  which is incredibly difficult, if not impossible   to get right. Yes, real life is messy, and  capturing that seems completely hopeless. Until scientists tried to write a computer  simulation to do this 11 years ago,   and this was the result. Wow, this is incredible.   Beautiful water droplets merging and splitting.    But it got better. Multi-material simulation  of…a bunch of melting bunnies was also possible. So, why doesn’t everyone just use this instead?   Amazing quality games and movies await! Well,   not quite. It has a big problem: when we give it  larger-scale scenes, it takes…forever. Literally   forever, because the algorithm can hang,  and never finish. So, amazing research,   but not quite there yet. However, it was so  difficult to beat, we’ve been waiting for 11   years now for a research paper that could get the  job done. It seemed like it would never happen,   but now, hold on to your papers Fellow  Scholars, because it is finally here. Let’s see what it can do. Holy mother  of papers! Look at that. A huge bunch of   bubbles with a 1,000 different materials. Yes!   Each bubble is treated as a distinct material,   not just some colored texture slapped onto it.   And they merge and pop beautifully. But it gets   better, because this is Two Minute Papers, and it  always gets better. Look! This is a simulation,   so they also produced an opaque view  of what is happening inside. And it   is beautiful beyond words. Wow. It looks a  bit like a molecular simulation. Loving it. Now, here’s a crab, but you know what  is better than a crab? Of course,   5 crabs! Let’s throw them together, now this  is 5. 3 million triangles and 72 different   materials. Absolutely impossible to do. Now, we  are going to cut through them, and look inside,   and see if we see garbled up geometry, or nice  separation. And…go! Wow. Look at that. Look at   that! Goodness! This is cleaner than a  freshly washed window in a Pixar movie. You know what? Now let’s use this knowledge,  and observe this what they call normal flow,   where we blow things up. The spheres  fill up the space beautifully,   the wireframe view reveals how difficult and  complex this piece of geometry is. And now,   let’s do this slicing operation as with the crabs. And…whoa! The key part here is that  the volume is under extreme pressure,   it expands until it perfectly fills the space. And  when we look into it, I see watertight geometry.    No overlaps, no missing faces, no tears.   And all this under extreme deformation. So, how on Earth is all this possible? This looks  like black magic! Well, this work is coming from   Chris Wojtan’s research group in Austria,  and he is a master of fluids and topology. And the research paper explains it,  but it is written for experts. I’ll   try to explain it in simple words. But  first, listen, you’ll love this one:   to summarize, it replaces explicit  collision-driven mesh surgery with a   local implicit reconstruction step that converts  self-intersections into topological changes. Okay, what the heck does all  this mean? Dear Fellow Scholars,   this is Two Minute Papers with Dr.   Károly Zsolnai-Fehér. Dr. Carroll. So, previous work. Imagine that you are making  a movie where every time two bubbles touch,   you stop everything, take a pair of  scissors, cut and glue everything   together until it looks good. Then, advance  one pitiful frame, and do it again. This is   the collision-driven mesh surgery part. No  wonder it hangs when you give it a big scene! Okay, so what the new one does instead is  it creates a simulation that does not need

cutting and gluing, because…drumroll…it heals  itself. Automatically and on the fly! Crazy! That means that you can even give it defective  geometry, and it can not only deal with it,   but heal it too! For instance, if you  give it these poor little bunnies,   their little rumps are going to get healed too. But it gets better. Look! It finally runs in  finite time. So yes, it will be done within   our lifetime, how cool is that? I’ll tell  you exactly how long it takes in a moment. Now please drop a like, subscribe,  hit the bell icon and leave a really   kind comment to help save these  papers, because they are amazing,   and absolutely nobody is talking  about them. We have to save them. Ok, so in practical terms, it is 7-10 times  faster than the previous technique. So previously,   an all-nighter render runs in a lunch  break. Glorious! And it always finishes.    Or otherwise this would have to be an  infinitely long lunch break. And scales   to huge scenes and broken geometries as  well. It can handle bubbles bigger than   the one inflating the AI stock market right  now! Hooray! This is absolutely incredible   and it is going to change everything. You  saw it here first on Two Minute Papers. Now, not even this technique is perfect, it works  with a sparse background grid, this grid has a   certain resolution, like pixels in an image, but  in 3D. And if we have a hole that is smaller than   our pixels, that is, one grid cell, it will miss  it. If you catch it doing that, you can counteract   it with higher grid resolution. And just one  more paper down the line, I bet this will also be   solved. A really advanced paper explained in  really simple words. What a time to be alive! So, this heals your meshes, no more  craters - subscribe to Two Minute Papers.