Help with trig and stuff please

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Post » Thu Sep 17, 2009 2:21 pm

I'm fine with trig on paper, but I somehow have a mental block trying to apply it to my game, so maybe you guys can help :)

What I need is best summed up in this diagram:


In other words, the X and Y of the spot 30 (for example) pixels above the plane, but 'up' is the direction of the plane's floor to roof rather than ground to plane :P

So basically I need what to put in the X and Y fields of 'add force towards'.
Hope you can help :)
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Post » Thu Sep 17, 2009 2:27 pm

AAaaaaand I seem to have figured it out (with the help of Hempuli on IRC) about ten seconds after I post.

Well, may as well make sure this is the 'best way' to do it.

In X I have: Sprite.X-cos(Sprite.Angle+90)*30

In Y I have: Sprite.Y+sin(Sprite.Angle-90)*30

And 100 in Force.

Is this the best way?
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Post » Thu Sep 17, 2009 6:04 pm

That is correct, yes, but this formula is actually a little simpler:

X = Sprite.X + cos(Sprite.Angle - 90) * 30
Y = Sprite.Y + sin(Sprite.Angle - 90) * 30

The only change for the Y coordinate is that "cos" is changed to "sin". Everything else stays the same.
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Post » Fri Sep 18, 2009 4:49 pm

Thanks.
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