
The Secrets of Cloth Simulation in Alan Wake - Red_Tarsius
http://www.gamasutra.com/view/feature/132771/the_secrets_of_cloth_simulation_in_.php
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drzaiusapelord
Is this why so many games have some muscle-bound guy/gal in near skin-tight
clothing be the lead? I never knew cloth simulation was such a difficult
problem. I remember Lucas talking about this stuff when he was making the
prequels, but I assumed everything has been long solved by now.

That said, I was pleasantly surprised in GTAV that when your character gets
wet, his clothing and hair look wet and stay wet for a bit. I don't think I've
seen that before.

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mortenjorck
Wet clothes in GTA V is actually a shader effect rather than a geometry
effect: It's just adding a specular shader to the normally diffusion-shaded
surface so it looks like your suit, hoodie, or wife beater is soaked with
water. I'm pretty sure the geometry stays the same.

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santaclaus
I don't know about games, but in movies, at least, a common trick to make
simulations look wet is to simply increase the mass of the wet object. This
causes hair and clothing to drape.

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aaroninsf
Conspicuously missing (or I'm reading too fast), footage of the actual results
:P

[https://www.youtube.com/watch?v=s40yXGCcorE](https://www.youtube.com/watch?v=s40yXGCcorE)

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radley
Easier-to-see daytime view in the video

[https://youtu.be/s40yXGCcorE?t=3m29s](https://youtu.be/s40yXGCcorE?t=3m29s)

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amelius
The edges still make the whole thing look like polygons, which is a pity,
since the edges should not take that much computational effort to get right.

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santaclaus
It is interesting that they refer to the simulation system as 'Verlet Physics'
\-- that sort of constraint satisfaction system is called 'Position Based
Dynamics' in most of the graphics lit. This type of system is also used in
Maya's Nucleus and NVIDIA's PhysX. [1] is a nice overview.

[1] [http://matthias-mueller-
fischer.ch/publications/STAR2013.pdf](http://matthias-mueller-
fischer.ch/publications/STAR2013.pdf)

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TheLoneWolfling
They're calling it Verlet physics because they're using a Verlet scheme for
integration - which is a relatively elegant approach if you don't ever need
velocities.

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santaclaus
But it isn't really verlet, I don't think it will converge like a 'standard'
verlet implementation with constraints (like molecular dynamics cats use) -
the effective stiffness of the objects here is dependent on the time step.

