OpenEuphoria

Re: Anyone know anything about trigonometry?

• Posted by Chris Bensler <bensler at telus.net> Sep 06, 2001
• 431 views

Unless you really want it to be fairly accurate, I wouldn't worry about
calculating trajectories.
In fact, more often than not, I find it looks more realistic, taking the
approach I mention, rather than actually trying to calculate the trajectory.
Like others said, you need to consider gravity, resistance (friction and
wind force), inertia, mass, aerodynamics (that's being very petty :P).
If you were making a golf game, I would say that tracjectory calculations
would be crutial.

If you look at any fireworks demos, they should give you an idea of what to
do. Most use arcs for the path of the flare and the sparks, they will even
take into account GRAVITY and trajectory SPEED.
I haven't looked at the workings of the EU fireworks demos, but I suspect it
would be similar.
I know that there are numerous fireworks examples for BASIC, that
demonstrate how to do the arced paths.
The main concept is to change the position incrementally(the increment can
be whatever realistic value you choose), multiplying the increment by SPEED,
and subtracting (or dividing) GRAVITY every time. Once you've made your
calculation for that increment, you decrement SPEED. Eventually, speed will
be 0 and the trajectory will end.

For fireworks, I would have static values for increment and gravity, and
speed is random. For your purposes, speed wouldn't be random.

This should give you an idea of how to proceed

EG.
INCREMENT=10
GRAVITY=0.6
SPEED=50

while SPEED>0 do
    pos_x+=INCREMENT*SPEED*GRAVITY
    pos_y+=INCREMENT*SPEED*GRAVITY
    SPEED-=1
end while

Chris