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AppGameKit Classic Chat / Locate my wing positions after sprite rotated

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Scotty1973
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Location: Burton-on-Trent, uk
Posted: 30th Sep 2014 13:20
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Hi

Asteroids style game where you have a ship that can rotate and move.

I want to fire laser from wings of the ship. Ship is positioned using center of sprite offsets.

I can calculate the position at 0 degrees from the offset x,y of the ship sprite with no problems.
The question is this:-
How do I calculate these positions after the ship has rotated and moved?
Been trying to use sin and cos but not having much luck with it!
Scary maths ahead me thinks!!

Any help please

Scotty
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Markus
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Posted: 30th Sep 2014 13:41 Edited at: 30th Sep 2014 13:43
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the offset is the direction multiplied with distance.

something like this
dx=cos(angle) <- u can use +- angle for left right laser start point
dy=sin(angle)

offset
ox=dx*distance
oy=dy*distance

world coords
wx=shipx+ox
wy=shipy+oy

perhaps exchange sin/cos or the sign before.

AGK 108 (B)19 + AppGameKit V2 Alpha .. : Windows 8.1 Pro 64 Bit : AMD Radeon R7 265
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baxslash
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Posted: 30th Sep 2014 14:25
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Or you could use the built in commands for translating a pixel position on a sprite to a world position (assuming this is 2D?):
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Scotty1973
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Posted: 1st Oct 2014 07:21
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Cheers Markus and Baxslash for your responce.

I have used Markus' way which seemed to work fine for me.

It is a 2D thing baxslash but not too sure how those commands work, mind you it is 5am and i'm supposed to be getting ready for work lol.

Many thanks

Scotty
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Marl
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Location: Bradford, UK
Posted: 1st Oct 2014 14:06 Edited at: 1st Oct 2014 14:07
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...or you could make the laser from a sprite which rotates with the ship.

Saves a load of maths.

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Markus
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Posted: 1st Oct 2014 14:17 Edited at: 1st Oct 2014 14:18
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or modify the laser offset, u can set same pos/rot as ship.
the handle point can be outside image.
(its similar what Marl said.)
SetSpriteOffset( iSpriteIndex, x, y )

AGK 108 (B)19 + AppGameKit V2 Alpha .. : Windows 8.1 Pro 64 Bit : AMD Radeon R7 265
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Impetus73
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Posted: 1st Oct 2014 15:29
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I agree with rotating the laser with the ship.

----------------
AGK programmer
Did Amiga / AMOS programming in the 90's.
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Markus
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Posted: 1st Oct 2014 16:22
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+ ship need gun turret

AGK 108 (B)19 + AppGameKit V2 Alpha .. : Windows 8.1 Pro 64 Bit : AMD Radeon R7 265
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