# 3D Theory - Snooker - Rolling Contact

Imagine that the ball is rolling with no slipping. When it rotates by 1 radian then it will move a vertical distance equal to the radius of the ball (see definition of radian)

So:

v = r * w

where:

• v = linear velocity
• r = radius of ball
• w = angular velocity

So the angular velocity is directly linked to linear velocity.  Can we work directly from the linear velocity in our program, calculating angular velocity from linear velocity when required?

Of course, this assumes that there is no slipping.  For that to be true the linear momentum must be exactly matched to the rotational momentum.

### Direction

If there is no slipping then the direction of travel is related to the axis of rotation. For instance, if the ball is rotating about the y axis, then it will be travelling in the x direction.

Where I can, I have put links to Amazon for books that are relevant to the subject, click on the appropriate country flag to get more details of the book or to buy it from them.

Developing Games in Java

other games programming books

Commercial Software Shop

Where I can, I have put links to Amazon for commercial software, not directly related to this site, but related to the subject being discussed, click on the appropriate country flag to get more details of the software or to buy it from them.

 Dark Basic Professional Edition - It is better to get this professional edition This is a version of basic designed for building games, for example to rotate a cube you might do the following: make object cube 1,100 for x=1 to 360 rotate object 1,x,x,0 next x Game Programming with Darkbasic - book for above software

other commercial software

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