Cloth Model

Mass Spring Model The cloth model is represented by a grid of particles of known mass, connected by a series of spring-dampers.   There are three main types of spring which relate to the characteristics of cloth:

1. Structural  springs:  Handle  extension  and  compression  and  are  connected vertically and horizontally.
2. Shear springs: Handle shear stresses and are connected diagonally. 
3. Bend  springs:  Handle  bending  stresses  and  are  connected  vertically  and horizontally to every other particle.The springs are the structural elements of the model and resist the various loads that are applied to the particles.

Figure 1 below illustrates the three types of springsand how they are connected to the particles.

Figure 1

When the simulation is initiated, each spring’s rest length is set to the original length of the spring.  The mass values of the particles and the spring constants are defined by the user.  Additional information on simulationOnce the springs and particles are set up, the simulation is incrementally advanced by integrating Newton’s Second Law of Motion. When an environmental force, for example gravity, is applied to the particles in the model over a specified time step, it produces a resulting acceleration for each particle. This acceleration gives rise to a velocity which causes the particle to update its position.  The new position of each particle in turn causes a change in length to each connected spring-damper.  Hooke’s Law states that the extension of a spring is proportional to the applied force. By applying Hooke’s Law with the addition of damping calculations to reduce oscillations, a new force due to the springs can be calculated and applied to the simulation.   The combination of the particle and spring forces is integrated with respect to time to provide a new acceleration for each particle.