TheGameCreators - CodeBase

Category: Math / Physics

Version: 1.0

Information

Uploaded: 3rd Jan 2004 11:49

Modified: 1st Jan 1970 01:00

Author: Ianx

Summary

Reasonably accurate simulation of 10 balls dropping onto a hard surface in a gravity field, losing energy on each bounce

Full Description

My first db programme after downloading the trial last night. I'm pretty pleased with how easy it was to create something fairly accurate in physics terms. <br /> <br /> As it's my first piece of code comments are not only welcome, they're encorouged.

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

rem ========================================================

rem

rem Simple bouncing ball physics

rem

rem ========================================================

rem --------------------------------------------------------

rem Initialisations and set up

rem --------------------------------------------------------

hide mouse

autocam off

load sound "tin2.wav", 1

set display mode 1024, 768, 32

randomize timer()

num_spheres#=10

rem g# represents gravity

g#=1

rem e# represents the energy lost when a ball hits the floor

e#=0.8

rem edelta# represents an increase in the energy lost as the sphere loses momentum

edelta#=0.95

rem --------------------------------------------------------

sync on

sync rate 0

rem --------------------------------------------------------

rem Create the spheres and position the camera

rem --------------------------------------------------------

for x = 1 to num_spheres#

make object sphere x, 100, 25, 25

position object x, 200*x, 500, 100

set object smoothing x, 100

next x

rem The calculations on the x position attempt to put the camera in a

rem central position depending on how many spheres we have

position camera ((num_spheres#/2)*200)-800, 150, -800

point camera ((num_spheres#/2)*200), 150, 0

rem A slightly oblique angle shows the effect off better

rotate camera camera angle x(), 30, camera angle z()

rem --------------------------------------------------------

rem Initialise the main variables

rem --------------------------------------------------------

rem

rem vY# is the velocity the sphere is travelling in the Y direction

rem pY# is the sphere's position on the Y axis, similar for pX# and pZ#

rem e# is explained above

dim vY#(num_spheres#)

dim pY#(num_spheres#)

dim e#(num_spheres#)

dim pX#(num_spheres#)

dim pZ#(num_spheres#)

for x = 1 to num_spheres#

vY#(x)=1

pY#(x)=object position Y(x)

pX#(x)=object position X(X)

pZ#(x)=object position Z(x)

rem We want to give the spheres a different amount of "bounciness"

e#(x)=90+rnd(9)

e#(x)=e#(X)/100

next x

rem --------------------------------------------------------

rem Main program loop

rem --------------------------------------------------------

rem

rem Continue looping until there's virtually no energy left

rem in any of the sphere

Gosub Get_Max_e

while Max_e#>0.1

for x = 1 to num_spheres#

rem Move the sphere by the velocity amount

pY#(x)=pY#(x)-vY#(x)

rem Apply gravity to the velocity (this is really the acceleration)

vY#(x)=vY#(x)+g#

rem If the sphere has hit the floor, reverse its direction, applying

rem a factor for lost energy

if vY#(x)>pY#(x)

vY#(x)=-1*vY#(x)*e#(x)

e#(x)=e#(x)*edelta#

rem Play a sound when the sphere hits the floor, but adjust the

rem volume according to how much energy the sphere has

vol=e#(x)*100*1.4

if vol>100 then vol=100

set sound volume 1, vol

rem Pan the sound so that the left-most ball comes out of the left speaker etc

set sound pan 1, ((x-1)*200/(num_spheres#-1))-100

play sound 1

rem Scale the sphere in the y direction as it hits the floor to simulate it

rem squashing slightly as it impacts. The amount depends on the energy the

rem sphere has ie more energy = more "squashing"

scaley=185-(e#(x)*100*1.4)

if scaley > 100 then scaley = 100

scale object x, 100, scaley, 100

else

scale object x, 100, 100, 100

endif

position object x, pX#(x), pY#(x), pZ#(x)

sync

next x

gosub Get_Max_e

endwhile

show mouse

exit prompt "All done", "Bouncing balls"

Get_Max_e:

rem Wouldn't it have been great to make this a function? However you can't access global

rem variables in functions, and you don't seem to be able to pass arrays as parameters so...

CodeBase - Ball physics

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Author Name:	Ianx
CodeBase Entries:	2