Here''s a question for someone that has a better knowledge of trig etc than i do... I have 2 points, one at (a.x,a.y) and the other at (b.x,b.y) They can be anywhere on the screen I want to fire a projectile from point a to point b The projectile will have an x speed and a y speed. How do i find what the x speed and y speed of the projectile should be? I''m not worried about how fast the projectile travels, as once i have the speed values, they can be multiplied by the same factor to speed it up. ---- Gareth Williams gareth@fatweb.org ----

So, we have two points:

A                  B

and you want two components of velocity (x and y) such that a projectile with those velocity components will travel from A to B.

This is very easy:
Total x distance = b.x - a.x
Total y distance = b.y - a.y
Total linear distance = sqrt(((b.x - a.x) * (b.x - a.x)) + ((b.y - a.y) * (b.y - a.y)))

So in order to get your projectile to travel from A to B you need to set
projectile.xSpeed = (xDistance/linearDistance) * projectileSpeed
projectile.ySpeed = (yDistance/linearDistance) * projectileSpeed

I hope I haven't made any glaring mistakes!

EDIT: html tag brackets wrong

Edited by - Enigma on October 26, 2001 7:22:37 AM

Thanks alot!

I knew it would be simple really, but I just lack the ability to be able to think mathematically beyond a certain level of difficulty

It''s gonna make learning more complicated 3D stuff nigh on impossible :/

Oh, uhhh, check out the project this applies to

Thanks again



----
Gareth Williams
gareth@fatweb.org
----

LOL I just noticed that this is simple pythagorus!

Damn easy when you think about it

----
Gareth Williams
gareth@fatweb.org
----

xspeed = sin(angle) * speed;
yspeed = cos(angle) * speed;

object.x += xspeed;
object.y += yspeed;

Some simple trig pseudocode