3D Cloth Simulation
-
Upload
maxwell-dickerson -
Category
Documents
-
view
62 -
download
2
description
Transcript of 3D Cloth Simulation
3D Cloth Simulation
Eva SchifferAaron Bryden
Goal
Learn about methods of 3D cloth simulation
Implement a simulation with:
point masses and a simple spring system
the choice of explicit, and implicit integration
Existing methods, springs
Cloth is modeled as a system of point masses
All springs use the same force equation
Three types of springs:
structural springs
sheer springs
bend springs
( )llkxkf ssspring −−=−= 0
( )21 vvkvkf dddamp −−=−=
Equations from Steve RotenBerg’s Class’s notes
Existing methods,explicit integration
set time step, s
use state(t + s) = state(t) + s * forces(state(t), t)
the state includes position and velocity
must calculate each step by s
good: simple to implement, okay for very high damping factors
bad: slow, needs short s and/or high damping or it will “explode”
Existing methods, implicit integration
use state(t + s) = state(t) + s * forces(state(t+s), t+s) or
This means that we have to solve for values of deltax and deltav
Uses modified conjugate gradient solver that exploits the sparsity that results from each node only being connect to nearby nodes.
What we did
Basic spring forces
particle system and simple explicit integration with generative forces inspired by “Particle System Dynamics” from SIGRAPH 2003 course notes
Implicit Integration based on “Large Steps in Cloth Simulation” by Baraff and Witkin, 1998.
Extended particle system and wrote implicit integration based on Hamilton Chong’s Code. Specifically, using his modified conjugate gradient solver and his filling of the df_dx and df_dy matrices based on position and velocity to have the proper sparsity characteristics.
Results
Explicit is slow to calculate, due to requiring a very small time step, and requires tuning the time step depending on the spring constants and damping factors to keep it from degenerating into chaos
Implicit is fast and does not degenerate with as small of a timestep. Each step takes longer to calculate, but the degree to which large time steps may be taken results in a significant time reduction to simulate a certain amount of time.