A cloth simulation written using Microsoft XNA 3.0. This uses a series of springs (structural, shear and bend springs) and constraints. The two top corners of the cloth is pinned using a point constraint and can be controlled by the user.

The main building blocks of a good cloth simulation are the three kinds of springs:

• Structural springs: These are the main springs in the cloth that are placed along each quad edge
• Shear springs: These are springs which helps maintain the diagonal shape of the cloth and are placed along the two diagonals of a quad
• Bend springs: These are springs which help to control the bending of the cloth and are placed like the structural springs but connects vertices that are two vertices apart

To illustrate how the different kinds of springs are important, I have created some videos to show how the cloth will look like without some of them.

The video below shows how a cloth simulation will look like without using shear and bend springs (i.e. using only structural springs). The cloth tends to lose its shape very easily, as can be seen when the two corners are brought close together.

The video below shows how a cloth simulation will look like without using bend springs (i.e. using only structural and shear springs). The cloth looks decent when fully stretched out, but starts to show signs of poor deformation when it bends. It tends to fold too easily and sometimes even stays folded (e.g. at the end of the video).

Constraints are another important building block of a good cloth simulation. Length constraints help to maintain the distances between the vertices and can be thought of as a spring of infinite stiffness. The video below shows how a cloth simulation will look like without using length constraints. The cloth tends to be very elastic and quite unstable as the different springs fight against one another.

For more detailed information and implementation techniques, please check out my soft body tutorial.