Question about Projectiles

[shinobitaichou]

I was just wondering what type of mathematical computations/physics I need to know for determining a projectile's path and trajectory.

[mixedtrigeno]

the x and y initial position of the bullet
the speed
the path it will travel through either x and/or y
the destination of the bullet
and the condition the will trigger the bullet

[buk09]

to do this all you need is trig...
M
............./|
.........../..|
........./....|
......./......|Y
...../........|
O /A_____|
X
take this badly drawn ascii triangle were 'O' is the origin of the shot 'M' where the aimer/mouse is and 'A' is the angle.

what you need to do is find 'A'

to do this you use

atan2(Y,X)

(or if its based of a characters rotation use the characters rotation as A)

then to get the projectile to move:

Math.sin(iAngle * (Math.PI/180))

this will give you the amount you need to increment the x value by every frame

Math.sin(iAngle * (Math.PI/180))

for the y increment:

Math.cosn(iAngle * (Math.PI/180)) *-1

so all up (pretend that this is based off char rotation and the

addEventListener(Event.ENTER_FRAME,eFrame)
addEventListener(MouseEvent.MOUSE_DOWN, shootOn);

function eFrame(evt:Event){
     projectile .x+=xInc
     projectile .y+=yInc
}


function shootOn(evt.MouseEvent){
     var xInc:Number = Math.sin(charRotation* (Math.PI/180)) 
     var yInc:Number = Math.cos(charRotation* (Math.PI/180)) * 1;
}

of course you realise that you will need to do that properly but thats the general gist of that.

for other things like gravity just do somthing like

yInc+=gravity

for bouncing projectlies

if (projectile.y == ground){
     yInc = -yInc * bounceDecay // 0.4 or something like that
}

i hope that helps i will once again say that it is all really rough so dont dig into me for that its just there to give you an idea of what to do

[shinobitaichou]

Thank you, buk.