TheGameCreators - CodeBase - Inertial movement using vectors (asteroids-style)

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Category: Math / Physics

Version: 1.0

Information

Uploaded: 12th Oct 2003 23:06

Modified: 1st Jan 1970 01:00

Author: ESC_

Summary

drifting inertial movement with friction

Full Description

This is just a quick snippet I put together for people who want to create drifting and momentum in their games using vectors.

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

remstart

How to use vectors-making a small asteroids-style movement demo

By ESC

The idea behind this is quite simple

A vector is a unit that can store both magnitude and direction (5 feet north, for example)

In this snippet, there are two vectors, the main vector of the ship, and another 'component'

vector which will be added to the main vector.

How does vector addition work?

|....................

|......cb............

|.....c.b............

|....c..b............

|...c...b............

|..c...aa............

|.c..aa..............

|c.aa................

|aa..................

if vector a was added to vector b, logically they would add to be vector c.

All you need to do is first add the x components of the two vectors, and then add the

y components, and voila, you have your new vector!

remend

`initilization

set display mode 1024,768,32

set window off

backdrop on

color backdrop 0

sync on:sync rate 60:hide mouse

`load in ship sprite image

load image "ship.bmp",1

`x & y coords and angle of the ship

x#=300

y#=300

angle#=0

`component vector magnitude(acceleration of ship)

accel#=0.1

`friction value-must be >1

`the closer it is to 1, the less friction there is

`This is because the main vectors of the ship are devided by this value

friction#=1.005

`turn rate of ship

turnrate#=2

`set up a vector type

type vector

x as float

y as float

endtype

`set up the ship's main vector

shipv as vector

shipv.x=0

shipv.y=0

`setup component vector for vector addition

comv as vector

comv.x=0

comv.y=0

`make the sprite

sprite 1,x#,y#,1

offset sprite 1,49,37

`rotate the ship

if rightkey()=1 then angle#=angle#-turnrate#

if leftkey()=1 then angle#=angle#+turnrate#

angle#=wrapvalue(angle#)

rotate sprite 1,wrapvalue(-1*(angle#+180))

`calculate the component vector (added to the main vector if upkey is pressed)

comv.x=sin(angle#)*accel#

comv.y=cos(angle#)*accel#

`ship movement

if upkey()=1

`add the vectors together to produce a final vector

shipv.x=shipv.x+comv.x

shipv.y=shipv.y+comv.y

endif

`calculate friction

shipv.x=shipv.x/friction#

shipv.y=shipv.y/friction#

`check to make sure ship isn't offscreen (that way you can't lose the ship

if x#<0 then x#=screen width()

if x#>screen width() then x#=0

if y#<0 then y#=screen height()

if y#>screen height() then y#=0

`reposition the ship

x#=x#+shipv.x

y#=y#+shipv.y

sprite 1,x#,y#,1

set cursor 0,0:print screen fps()

sync

loop

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Author Name:	ESC_
CodeBase Entries:	1

CodeBase - Inertial movement using vectors (asteroids-style)