2D Bullet Tracking - GameCreators Forum

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kklouzal

14

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Joined: 15th May 2009

Location: Arizona

Posted: 26th Oct 2012 00:51

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With known coordinates of my Target and Shooter I need to fire a Bullet from the Shooter at the Target. I'm doing this in 2d to simplify things, I believe my math is a little wrong though.

I create a sprite at my Shooter, have it rotate to face the target, then move towards it. The bullet gets about half way then starts to spazz out.

+ Code Snippet

void Projectile::SeekTarget(void)
{
	int x2 = dbSpriteX(targetNum);
	int y2 = dbSpriteY(targetNum);

	int x1 = dbSpriteX(sNum);
	int y1 = dbSpriteY(sNum);

	float x = x2-x1;
	float y = y2-y1;

	float rad = dbATANFULL(y, x);

	float angle = rad * 180 / PI;

	dbRotateSprite(sNum,angle-90);
        dbMoveSprite(sNum,1);
}

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kklouzal

14

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Joined: 15th May 2009

Location: Arizona

Posted: 26th Oct 2012 06:47

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I've searched the forum on this and can't find anything..

Basically I just need to rotate the sprite towards a set X & Y coordinates.

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DeadTomGC

13

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Joined: 11th Aug 2010

Location: LU

Posted: 26th Oct 2012 09:51

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You can use dbATAN(Y/x) (any ARC tangent function will do) where y is the distance the point is in the y direction and x is the distance the point is in the x direction from the thing you are rotating.

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kklouzal

14

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Joined: 15th May 2009

Location: Arizona

Posted: 26th Oct 2012 17:12

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Thank you, I'm getting a little confused can you give me an example?

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kklouzal

14

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Joined: 15th May 2009

Location: Arizona

Posted: 26th Oct 2012 22:08

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This is what I have so far, it's a little better but the bullets freak out about half way to the target

+ Code Snippet

	float x2 = dbSpriteX(targetNum);
	float y2 = dbSpriteY(targetNum);

	float x1 = dbSpriteX(sNum);
	float y1 = dbSpriteY(sNum);

	float x = x2-x1;
	float y = y2-y1;

	float rad = dbATANFULL(y, x);

	float angle = rad * 180 / PI;

	dbRotateSprite(sNum,angle-90);

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kklouzal

14

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Joined: 15th May 2009

Location: Arizona

Posted: 27th Oct 2012 20:52

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If the target is moving they wiggle like crazy; im confused

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darkvee

18

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Joined: 18th Nov 2005

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Posted: 27th Oct 2012 23:06 Edited at: 27th Oct 2012 23:08

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Just use this.

+ Code Snippet

        float x2 = dbSpriteX(targetNum);
	float y2 = dbSpriteY(targetNum);

	float x1 = dbSpriteX(sNum);
	float y1 = dbSpriteY(sNum);

	float x = x2-x1;
	float y = y2-y1;

	float angle = dbATANFULL(y, x);

	dbRotateSprite(sNum,angle);

darkvee

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