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issue with image placement in respect of another image

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#1kingpinzs  Members   -  Reputation: 109

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Posted 10 May 2012 - 02:05 PM

I am using XNA 4.0 and c#

how can I get an image to set its position according to the end of another image?

this is what I have so far

rocketPosition = players.Position;
rocketPosition.X += players.Position.X +40;
rocketPosition.Y -= players.Position.Y -370 ;
rocketAngle = players.Angle;
Vector2 up = new Vector2(0, -1);
Matrix rotMatrix = Matrix.CreateRotationZ(rocketAngle);
rocketDirection = Vector2.Transform(up, rotMatrix);
rocketDirection *= players.Power / 50.0f;

the rocket goes in the right direction but its starting position is wrong if I move the cannon

the code that moves the cannon

if (keybState.IsKeyDown(Keys.Left))
{
if(players.Angle > MathHelper.PiOver4-.3)
players.Angle -= 0.01f;
}
if (keybState.IsKeyDown(Keys.Right))
{
if (players.Angle < MathHelper.PiOver2)
players.Angle += 0.01f;
}

#2Jutaris  Members   -  Reputation: 478

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Posted 18 May 2012 - 03:15 PM

I accomplished this using something like this:

public Vector2 WeaponFireLoc
{
get
{
return Location + (WeaponDir * <X Offset at neutral angle, I used 5 but have small sprites>);
}
}
public Vector2 WeaponDir
{
get
{
Vector2 v = new Vector2(-1, 0);
v = Vector2.Transform(v, Matrix.CreateRotationZ(WeaponAngle));
if (v != Vector2.Zero)
{
v.Normalize();
}
return v;
}
}

The WeaponDir gets a normalized V2 (-1 -> 1) that points in the direction the weapon is aiming.
WeaponFireLoc returns a V2 that is N pixels down that direction from Location, where N is <X Offset at neutral angle, I used 5 but have small sprites>.

Hope that helps. I suspect it's not the only solution, and perhaps not the best, but it's worked for me.

Basic Flying Rules:Try to stay in the middle of the air. Do not go near the edges of it. The edges of the air can be recognized by the appearance of ground, buildings, sea, trees and interstellar space. It is much more difficult to fly there.

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