# Physics Reference

The following table describes each physics property type.

PropertyDescription

Mass

The mass of the fabric measured in grams per square meter.

Friction

Friction coefficient measures the amount the fabric resists sliding on the avatar. The lower the value, the easier it is for the fabric to slide. The higher the value, the more the fabric will hold its position.

• Minimum: Zero.

• Maximum: None. For guidance, values of 1 and 2 are high value.

If, for example, you have many layers of a dress that collide, you can reduce the friction to help reduce collisions.

The following image shows a fabric with a friction value of 0.3.

The following image shows the same fabric with a friction value of 0.2.

Thickness

The thickness of the fabric in millimeters.

The following image shows a fabric with a thickness value of 4.

The following image shows the same fabric with a thickness value of 1.

Bend

The bending rigidity or stiffness of the fabric measured in dynes per centimeter along the width and length. The lower the value, the less stiff the fabric. The higher the value the less the fabric bends, meaning the fabric is stiffer

Length is parallel to the grain line and width is perpendicular to the grain line.

• Minimum: Zero. For guidance, 5 is very low.

• Maximum: None. For guidance, 1,000 is high, with leather in the 1,000s.

The following image shows a fabric with a bend value of 20.

The following image shows the same fabric with a bend value of 10,000.

Stretch

The tensile stiffness or stretch of the fabric measured in Newtons per meter along the width and length. This property is the amount of force per unit of length needed to stretch a piece of fabric to twice its length (assuming the fabric is ideally or totally linear).

The lower the value, the more it stretches. The higher the value, the less the fabric stretches.

Length is parallel to the grain line and width is perpendicular to the grain line.

• Minimum: Zero. For guidance, 20 is low.

• Maximum: None. For guidance, 2,000 is high.

Stretch Linearity

When stretching a fabric, sometimes the fabric is easy to stretch at the beginning, then it becomes harder. Sometimes it is the other way around.

The higher the value, the more the fabric can be stretched at the beginning until the fabric's resistance stops the stretching. The lower the value, the less stretching the fabric allows before the resistance stops the stretching.

in general, elastic has higher linearity, knitted fabrics have intermediate values, and woven fabrics have low values.

A more technical description:

By how much the fabric can stretch along width and length before second order nonlinear effects begin to be noticeable.

If the value is 0, it is treated as fully linear, ie infinite linearity. Low values are for a less linear fabric, that will display nonlinear effects early, whereas high values are for a very linear fabric that can be stretched a lot without displaying such effects.

Length is parallel to the grain line and width is perpendicular to the grain line.

Shear

Shear rigidity is the stretch of the bias: the amount of force measured in Newtons per meter along the width and length needed to shear or distort a fabric to 45 degrees (assuming the fabric is ideally or totally linear).

• Minimum: 5

• Maximum: Around the same as the Stretch value.

Shear Linearity

The same as Stretch Linearity except that it refers to the bias sample.

Shrink

The amount by which a fabric shrinks or expands. If a user adds a value for shrink to a fabric it makes the fabric shrink (positive value) or expand (negative value).

Puffy Firmness

The amount of pressure, measured in dyns/cm^2 , needed to completely squeeze the puffy filling. For example, if you have 2cm of filling and you apply half of the Puffy Firmness pressure, the filling is compressed to 1cm.

Molded

This feature is primarily used for bras. If enabled, the user can select a type from the drop-down, and set a depth in centimeters. A molded fabric tries to maintain its own shape on the avatar. Note: You can best see this effect when using prepare mode.