Physics - Kinematics - Position

Prerequisites

If you are not familiar with this subject you may like to look at the following pages first:

Position Vector

We need a coordinate system to represent the position of an object. I have explained Cartesian and Polar coordinate systems here. The maths here is much easier if we use Cartesian co-ordinates, for 3 dimensions the position of any point (P) can be represented by 3 real (floating point or double floating point) numbers. This is usually represented as a vector of dimension 3:

Px
Py
Pz

where the 3 numbers represent the position in each of the, usually perpendicular, directions in an arbitrary reference frame. These Cartesian coordinates are usually called x (left & right), y (up and down), z (back and forward). On this site we are using a right handed coordinate system as described here.

Representing position in program

Position in 3D space can be held in a 3D vector (see class sfvec3f). For an example of how this might be used in a scenegraph node, see here.

Position of particle on solid object

If we have a particle of a solid object and we want to measure its position, then:

p = cm + r

where:
symbol
description
type
units
cm position of centre of mass of object vector m
r position of particle relative to object vector m
p position of particle in absolute coordinates vector m



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cover Engineering Mechanics - Includes Statics book and dynamics book below..

cover Engineering Mechanics Vol 2: Dynamics - Gives theory for rigid dynamics, aims to allow prediction of effects of force and motion. Includes rotating frame of reference. Lots of colour diagrams, I guess its college / University level.

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cover Dark Basic Professional Edition - It is better to get this professional edition

cover 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

cover Game Programming with Darkbasic - book for above software

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