TheGameCreators - CodeBase - Snooker / Pool / Billiards Physics

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Category: Math / Physics

Version: 1.0

Information

Uploaded: 28th Jan 2004 15:59

Modified: 1st Jan 1970 01:00

Author: Hamish McHaggis

Summary

Shows how to do realistic collision between billiard balls.

Full Description

Uses triganometry to bounce and speed up and slow down the balls as they fly around the table. Also works with the balls in close range like in a break. Turn the variable "numSteps" up if you find the balls dancing around each other (this would happen if you turned the speed up too much).

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

`===================

` Pool Physics Demo

` By Joseph Thomson

` 24/01/04

`===================

`If you use any of this code in any way please give

`credit to me for the original code.

`Position data for balls

DATA 100,240

DATA 400,240

DATA 421,230,421,250

DATA 442,220,442,240,442,260

DATA 463,210,463,230,463,250,463,270

DATA 484,200,484,220,484,240,484,260,484,280

DATA 505,190,505,210,505,230,505,250,505,270,505,290

`Ball type with velocity and position

TYPE ballType

xPos AS FLOAT

yPos AS FLOAT

xVel AS FLOAT

yVel AS FLOAT

ENDTYPE

`Number of balls and ball radius

numBalls AS INTEGER = 16

ballRad AS INTEGER = 10

DIM balls(numBalls) AS ballType

GOSUB placeBalls

`Walls

topWall = 10

bottomWall = 470

leftWall = 10

rightWall = 630

`Increase for increased accuracy

numSteps AS INTEGER = 30

tableFriction AS FLOAT = 0.025

wallDecay AS FLOAT = 1.0

shotAng AS FLOAT

shotPower AS FLOAT

mouseHold AS INTEGER

mouseHoldX AS FLOAT

mouseHoldY AS FLOAT

dist AS FLOAT

angleBetween AS FLOAT

ang1 AS FLOAT

ang2 AS FLOAT

vel1 AS FLOAT

vel2 AS FLOAT

velX1 AS FLOAT

velX2 AS FLOAT

velY1 AS FLOAT

velY2 AS FLOAT

totalVel AS FLOAT

SYNC ON

SYNC RATE 60

`Draw walls

INK RGB(255,255,255),0

BOX leftWall-1,topWall-1,rightWall+1,bottomwall+1

INK RGB(0,0,0),0

BOX leftWall,topWall,rightWall,bottomwall

`Do the movement of the balls and collision detection in steps, for increased accuracy

FOR l=1 TO numSteps

`Loop through all balls

FOR x=1 TO numBalls

`Move the ball

INC balls(x).xPos,balls(x).xVel/numSteps

INC balls(x).yPos,balls(x).yVel/numSteps

`Control the shooting of the ball

IF MOUSECLICK()=1

IF mouseHold = 0

mouseHold = 1

mouseHoldX = MOUSEX()

mouseHoldY = MOUSEY()

ELSE

shotPower = SQRT((mouseHoldX-MOUSEX())^2+(mouseHoldY-MOUSEY())^2)*0.2

IF shotPower > 100.0 THEN shotPower = 100.0

shotAng = 360-(180-ATANFULL(mouseHoldX-MOUSEX(),mouseHoldY-MOUSEY()))

ENDIF

ELSE

IF MOUSECLICK()=0 AND mouseHold = 1

mouseHold = 0

balls(1).xVel=SIN(shotAng)*shotPower

balls(1).yVel=COS(shotAng)*shotPower

ENDIF

`Replace the balls if space is pressed

IF SPACEKEY()=1

GOSUB placeBalls

ENDIF

`Control balls' collision with walls (rebounding and energy loss)

IF balls(x).xPos-ballRad < leftWall

balls(x).xPos = leftWall+ballRad

balls(x).xVel = -balls(x).xVel*wallDecay

ENDIF

IF balls(x).xPos+ballRad > rightWall

balls(x).xPos = rightWall-ballRad

balls(x).xVel = -balls(x).xVel*wallDecay

ENDIF

IF balls(x).yPos-ballRad < topWall

balls(x).yPos = topWall+ballRad

balls(x).yVel = -balls(x).yVel*wallDecay

ENDIF

IF balls(x).yPos+ballRad > bottomWall

balls(x).yPos = bottomWall-ballRad

balls(x).yVel = -balls(x).yVel*wallDecay

ENDIF

`Loop through all balls

FOR y=1 TO numBalls

`Don't check collision between the same ball

IF y<>x

`Get distance of balls from each other

dist = SQRT((balls(x).xPos-balls(y).xPos)^2+(balls(x).yPos-balls(y).yPos)^2)

`If they are touching

IF dist < ballRad*2

`Get the angle between them

angleBetween = ATANFULL(balls(x).xPos-balls(y).xPos,balls(x).yPos-balls(y).yPos)

`Move the first ball back where it was

DEC balls(x).xPos,balls(x).xVel/numSteps

DEC balls(x).yPos,balls(x).yVel/numSteps

`Get the angles of the balls velocities

ang1 = ATANFULL(balls(x).xVel,balls(x).yVel)

ang2 = ATANFULL(balls(y).xVel,balls(y).yVel)

`Get the speed of the balls velocities

vel1 = SQRT(balls(x).xVel^2+balls(x).yVel^2)*0.9

vel2 = SQRT(balls(y).xVel^2+balls(y).yVel^2)*0.9

`Work out the new velocities of the balls using trig

velX1 = SIN(angleBetween+90)*SIN(360-(angleBetween-ang1))*vel1+SIN(angleBetween)*COS(angleBetween-ang2)*vel2

velY1 = COS(angleBetween+90)*SIN(360-(angleBetween-ang1))*vel1+COS(angleBetween)*COS(angleBetween-ang2)*vel2

velX2 = SIN(angleBetween)*COS(angleBetween-ang1)*vel1+SIN(angleBetween+90)*SIN(360-(angleBetween-ang2))*vel2

velY2 = COS(angleBetween)*COS(angleBetween-ang1)*vel1+COS(angleBetween+90)*SIN(360-(angleBetween-ang2))*vel2

`Set the balls' velocities

balls(x).xVel = velX1

balls(x).yVel = velY1

balls(y).xVel = velX2

balls(y).yVel = velY2

ENDIF

NEXT y

`If the loop is on the last step...

IF l=numSteps

`Draw graphics

IF x=1

INK RGB(255,255,0),0

ELSE

INK RGB(255,255,255),0

ENDIF

CIRCLE balls(x).xPos,balls(x).yPos,ballRad

IF MOUSECLICK()=1 THEN LINE balls(1).xPos,balls(1).yPos,balls(1).xPos+SIN(shotAng)*shotPower*3,balls(1).yPos+COS(shotAng)*shotPower*3

`Control ball friction

totalVel = SQRT(balls(x).xVel^2+balls(x).xVel^2)

DEC balls(x).xVel,tableFriction*totalVel*(balls(x).xVel/totalVel)

DEC balls(x).yVel,tableFriction*totalVel*(balls(x).yVel/totalVel)

ENDIF

NEXT x

NEXT l

SYNC

CLS

LOOP

`Replace the balls

placeBalls:

RESTORE

FOR p=1 TO numBalls

READ balls(p).xPos

READ balls(p).yPos

balls(p).xVel = 0.0

balls(p).yVel = 0.0

NEXT p

RETURN

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Author Name:	Hamish McHaggis
CodeBase Entries:	14

CodeBase - Snooker / Pool / Billiards Physics

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