Simulating "Monsters University" by Samantha Raja (Pixar)
The next talk that we went to was the simulation behind Monster's University by Samantha Raja from Pixar Animation. This was a fascinating talk about a department in animation that I didn't even know existed. Simulation is basically a lot like animation but uses a lot more dynamics and looks closer into clothing and hair follicles to perfect the film further. It was very interesting to here about this due to this fact.
So, simulation is a department that adds just that extra little bit of detail into the animation especially if that scene included a lot of motion and it helps to bring the character to life more as 89% of the shots in this film included some form of simulation. Probably the most difficult part to the films simulation was dealing with the hair and the amount of hair. In the first film there was only one main character with fur wheras now here is as many as 20, and over 30% of the monsters had hair. Then in the original Monster's Inc film there was only ever one garment of clothing on Boo, whereas in University there are over 127.
The system that they use in the simulation process is called Fizt which was developed for the first Monster Inc film and it uses mass spring model implicit integration to do so.
The clothing pipeline that is implemented during this film starts in Maya and then converts into triangles when it is taken into Fizt as it warps the messes together in order to create the garment. Hair in the movie is all modeled in curves individually on Maya in which they made about two to three thousand for Sully's character. This may seem a lot but out of the whole 2 million he has it doesn't seem that much in the end. So in initial rendering you only ever see the key hairs and the complete render increases the amount by adding in the blank areas.
The stages that are taken to create something like this for a scene in an animation are:
- Layout without anything
- Improved animation
- Simulation
- Shading
- Lighting
The common challenges when it comes to simulation usually are physically based so they have to help it sometimes along the way as some clothing especially can have no-human proportions.
Pre-Simulation
There are a lot of different techniques that are used but kinsims and nails are a popular approach as in some scenes cloth is used in a dramatic way like stretched to extreme levels and the simulation doesn't know what to do so it just falls off, so they used pre-simulation to attach the cloth to the model so that it doesn't fall off the body and stretches with it instead and then in post simulation they are able to stop it from stretching the material too much. Glue is also another technique that is applied onto clothing around the neck and seems to stop clothing from slipping off rounder monsters where cloth wouldn't normally stay on.
Post-Simulation
There are also some things that can be added in post simulation that improve the way in which it looks and provides a few different effects so it can add those final touches to again improve the quality.
- Frame transformation
- Relaxee is a program they have for removing unpleasant bulges from clothing and other areas that need to be smoothed
- They also have a program where you are able to grab a certain amount of faces and freeze them so that they do not have influence and aren't going to move.
- Then they have a program where they can kill the influence the hair has under clothing so that in places where its underneath its removed and places where the hair is at the edges means that it bends around providing the best fit for clothing hairy monsters
When it came to the grass in the scene they borrowed a technique from Ratatouille were they flattened hair under the main characters hat and it would then bend back into place when it was removed. There were spheres in the bottom of all of the characters feet so that when they made contact with the grass they would flatten it and after a few momenta it would eventually pull back up into shape. This is also a similar technique that is used on Sully as he comes into contact with anything, especially when he moves, as the hair on his feet has to be pushed to one side as he takes a step.
Overall this was a fantastic talk and I learnt so much about a department in an animation studio that I didn't even know existed. It was so interesting as they are more focused than general animation ad they fine tune everything and can spend time looking at all of the little details that might not actually be even notices in the final film, but when you do notice it makes you wonder how they created and what effort went into producing such a complex little detail.
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