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REAL-TIME CLOTH SIMULATION

As part of my coursework for Technical Animation (CMU 15-664),  I simulated cloth behavior from scratch in Unity using C#.

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I achieved this  using the Verlet Integration method as described in the paper Advanced Character Physics by Thomas Jakobsen.

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Got it to run at around 50 fps. Most GIF examples below have been sped up for the presentation.

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Sim_00_Basic.gif

  • [above] Basic example of the cloth moving under gravity.

  • The demo runs at around 50 fps real time

Sim_00_Collision_0.gif

  • [above] Cloth moves under gravity, collides with sphere and slips down

  • Used Rigidbodies in Unity to detect the collision; applied force at the point of contact perpendicular to the plane of contact

Sim_00_Collision_1.gif

  • [above] Forcible collision of the sphere with the cloth still under gravity

  • Cloth recovers its shape

Sim_00_Collision_2.gif

  • [above] Another forcible collision of the sphere with the cloth still under gravity

Sim_00_Collision_3.gif

  • [above] If you too fast with the collision, sometimes the sphere goes through the cloth, and things go haywire.

Sim_00_Collision_4.gif

  • [above] Collision with a differently shaped object - a cube

Sim_00_Collision_5_Cube0.gif

  • [above] Ramming the cube into the cloth, which recovers shape

Sim_00_Collision_5_Cube1.gif

  • [above] Again, sometimes the cube goes through if the action is done too fast

Sim_00_Collision_7_Floor0.gif

  • [above] Contact with ground; the two pinned particles are unpinned at some point.

Sim_00_Collision_8_Floor1.gif

  • [above] Cloth falls on sphere, the ground and slips down under gravity

Sim_00_Collision_9_MorePart.gif

  • [above] Increased the number of particles from 100 to 400 in this one. The result was considerably slower.

Sim_00_Collision_9_SelfColl.gif

  • [above] Tried to make the cloth collide with itself

  • The Rigidbodies help with collisions among particles

Sim_00_Collision_10_Stiffness.gif

  • [above] Increased the stiffness from 0.5 to 1

  • Some particles are a little off

Sim_00_Collision_11_Timestep.gif

  • [above] Increased the time step value

  • The cloth sags a little more

Sim_00_Collision_12_One_Iter.gif

  • [above] Reduced the number of iterations form 15 to 1

Sim_00_Wind.gif

  • [above] Cloth acting under wind forces; stopped gravity for this one.

Some Notes:

  • Used a procedurally generated mesh in unity

  • Vertices are updated every frame and 

  • Timestep of 0.025

  • Iteration count kept at 15

  • All particles assumed to be of mass 1

  • Stiffness value for particles used as 0.5

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