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I am making a side scroller shooting game. I currently have my character shooting horizontally to the right. I would like to get him shoot anywhere on the screen.

I understand that I should use atan2 to figure what angle my bullet will be shot at but I am confuse how to implement it into my game.

My question is how do I call my coordinates of the touch on the screen into atan2? Do I place this in my touch command codes or the class for my projectile. Lastly do I need to do another atan2 for speed?

user2106015
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2 Answers2

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First you need the vector of your player

P = (a, b)

And the position of your shooting point

T = (x, y)

This then gives us a vector from P to T, (x - a, y - b). By taking

angle = atan2 (y-b, x-a)

From there, it depends how you are implementing your shooting.

To reiterate, all atan2 does is finds the angle, so

do I need to do another atan2 for speed

depends on whether you want to have the projectile moving at a different speed depending on angle. In fact, you only really need the angle if you are rotating your projectile, otherwise you can just move it along the vector (if it is a circle, doesn't matter what way it is facing!)

T. Kiley
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  • oh ya they are going to round but right now they are just rectangular pixels. I am still a little confuse on how you call for the coordinates of where you touch – user2106015 Feb 27 '13 at 03:15
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You don't need any trigonometry and you should not use it, as it is slow, inaccurate and full of sign (+/-) cases to get wrong.

You can probably do everything you need with linear algebra. Use vectors, not angles.

Kris Van Bael
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