Path: chuka.playstation.co.uk!news
From: richard.cutting@virgin.net (Richard Cutting)
Newsgroups: scee.yaroze.beginners
Subject: Re: angles, angles
Date: Wed, 18 Nov 1998 10:01:01 GMT
Organization: PlayStation Net Yaroze (SCEE)
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Message-ID: <3652971c.228584498@news.playstation.co.uk>
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On Tue, 17 Nov 1998 21:50:40 -0000, "Darren Jackson"
<darren@tang.globalnet.co.uk> wrote:

>HHmmm...
>
>The previous message isn't quite right, I am confusing myself at the minute
>!!
>
>The thing is how do I get the correct x and y values according to the angle.
>I know that x and y can only be integers but I need to know how many pixels
>across for every one up, for example. ( I have had a hard day at work and I
>trying to figure this out now!!).
>
>Darren
>
>

To compute the trajectory the following bit of maths is used;

xv = sin( angle ) * magnitude
yv = cos( angle ) * magnitude

( where angle is the angle relative to the horizon and magnitude is
the overall speed of the sprite in pixels per game cycle )

If you apply xv and yv to your sprites x and y co-ordinates the sprite
will move in a straight line path from its point of origin.

To get around the floating point problem you'll need a fixed point
trig library.   There are a couple floating around, two I know of can
be found at http://www.netyaroze-europe.com/~shaughnj or
http://www.netyaroze-europe.com/~nslaven

Richard.