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Table Of Contents

166 FORCE FIELDS

DYNAMICS

FORCE FIELDS 167

Field Tab

The Field tab contains

parameters for dening the

drag’s type, direction and

strength.

On the Field tab you can dene the type of drag (angular, linear or axial) as well as

its direction and strength.

Mode

Select the type of motion which the drag should affect: Linear, Angular or Axial.

Linear

The drag will affect linear motion, i.e. motion which changes the location of the body.

Linear drag will be applied regardless of the direction in which the object is moving.

Angular

This type of drag will decelerate rotating bodies.

Axial

The Axial mode breaks the following law of physics:

Drag will always be applied in the opposite direction to the body’s motion.

The Axial mode breaks the law by allowing you to specify the direction of the drag

(under Direction). Although it dees real world physics, the Axial mode helps you to

take short cuts as demonstrated in the example below.

Suppose you want to simulate a soft ball being thrown at a wall. To accomplish this,

you could use a drag eld to bring the ball to an abrupt halt in the wall region, plus

a gravity eld to accelerate the ball towards the ground after it has hit the wall.

Although a Linear drag eld would be able to halt the ball as it nears the wall, the

eld would in addition prevent the ball from accelerating towards the oor under

gravity. The ball would remain stuck to the wall.

The solution is to use the Axial eld, which will exert drag in a dened direction only.

By setting the direction of the Axial eld force to the opposite direction of the balls

initial motion, the drag will stop the ball as it nears the wall yet it will not oppose

the downwards motion. The ball will be allowed to fall to the oor.