# Formula Needed For Artillery Program

1. Sep 30, 2005

### MBMorrow

Hi,
I recently wrote a text version of the old DOS Artillery Duel (or Atari's Cannon Duel) game. In this version, you play against the computer and can control the (projectile) angle and velocity. I'd now like to add one more dimension whereby the height of the cannons randomly changes for each game instantiation. The changes to the math formula is where I need help. The main calculation is in the shot.awk script below. I've also included the other two routines in this game for anyone interested.

cannon.ksh - main program written in Korn Shell. Computer and human take turns shooting at one another

gettarget.awk - a simple awk script to get the target location (in this case the target is your computer enemy)

shot.awk - this is the one where the each angle/velocity are calculated to produce the cannon shot. I have read alot on physics and gaming forums but just don't quite understand the math to add in the variable factor for the elevation of the cannon. I don't really need help with the programming. Just the math.

Thanks if you can help! -Matt

cannon.ksh
-----------
#! /bin/ksh

currentshot=0
keepshooting=1

# Computer variables
comp_angle=45
comp_hi=100.00
comp_low=1
currentguess=50.00

target=awk -f gettarget.awk

# Set level of difficulty
echo " "
echo "Select a level of difficulty: "
echo " "
echo "(e)asy: Displays both computer and human parameters"
echo "(m)edium: Displays only human parameters"
echo "(h)ard: Displays only + or - for human"
echo "(v)ery hard: Same as hard but does not even show you the distance to enemy"
echo " "
read difficulty
if [ "$difficulty" != "v" ] then echo " " echo "Target distance:$target"
fi
echo " "
echo "Input angle (0-90) and velocity (1-100)"
echo " "

while [ $keepshooting -eq 1 ] do currentshot=expr$currentshot + 1

#
# Human shot
#

echo " "
read parms

angle=echo $parms | awk ' { print$1 } '
velocity=echo $parms | awk ' { print$2 } '

distance=awk -f shot.awk $angle$velocity

if [ $distance -eq$target ]
then
echo " "
echo " "
echo " "
echo " "
echo " "
banner "BOOM!"
echo " "
echo "You hit the target at $distance feet in$currentshot shots! "
echo "Computer was using $comp_angle$currentguess"
echo " "
keepshooting=0
else

echo " "

if [ $distance -gt target ] then delta=expr$distance - $target if [ "$difficulty" = "e" ] || [ "$difficulty" = "m" ] then echo "+${delta}"
else
if [ "$difficulty" = "h" ] || [ "$difficulty" = "v" ]
then
echo "+ you overshot"
fi
fi
else
delta=expr $target -$distance
if [ "$difficulty" = "e" ] || [ "$difficulty" = "m" ]
then
echo "-${delta}" else if [ "$difficulty" = "h" ] || [ "$difficulty" = "v" ] then echo "- you undershot" fi fi fi fi # # Computer shot # # Only take a shot if the human didn't just hit us if [$keepshooting -eq 1 ]
then
distance=awk -f shot.awk $comp_angle$currentguess

if [ $distance -eq$target ]
then
echo " "
echo " "
echo " "
echo " "
echo " "
banner "BAM!"
echo " "
echo "The computer got you at $comp_angle$currentguess in $currentshot shots! Distance:$target"
echo " "
keepshooting=0
else

echo " "

if [ $distance -gt target ] then delta=expr$distance - $target echo " " if [ "$difficulty" = "e" ]
then
echo "Computer: $comp_angle$currentguess +${delta}" else echo "Computer missed!" fi # low routine from guess comp_hi=$currentguess
# need awk for fractions
currentguess=echo $currentguess$comp_low | awk ' { printf("%2.2f",($1+$2)/2 ) } '

else
delta=expr $target -$distance
echo " "
if [ "$difficulty" = "e" ] then echo "Computer:$comp_angle $currentguess -${delta}"
else
echo "Computer missed!"
fi

# hi routine from guess
comp_low=$currentguess # need awk for fractions currentguess=echo$currentguess $comp_hi | awk ' { printf("%2.2f",($1+$2)/2 ) } '  # Check for 99.99 (in order to guess 100) - must convert to int tcurrentguess=echo$currentguess | awk ' { printf("%d",$1*100) } '  if [$tcurrentguess -eq 9999 ]
then
currentguess=100
fi
fi

fi
fi

done

exit

gettarget.awk
-------------
BEGIN {
trand=srand()
target=int(1000*rand())+1
printf("%d\n",target)
}

shot.awk
---------
BEGIN {

angle=ARGV[1]
ARGV[1]=""
velocity=ARGV[2]
ARGV[2]=""

gravity=(9.8*-1)

# convert angle to degrees
angle=(angle*3.14159265)/180

# original vector for x and y
vx=velocity*cos(angle)
vy=velocity*sin(angle)

# Midflight (velocity=0, no rise, no fall)
mf=(vy*-1)/gravity

# apex - used for graphics
#apex=(vy*mf)+(0.5*gravity*(mf*mf))

# Fullflight is total time of flight
ff=mf*2

distance=vx*ff

printf("%3.0f\n",distance)
}

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted