Rotate Texture in function of player position

问题

I'm making a 2d game that consists in a plane fighting against spaceships trough missiles, i want the spaceships to rotate in function of the player position, so that they are always facing the player with the "head". The player can move freely in the y and x directions. THe player and the spaceships have a Vector2 pos variable, that corresponds to their actual position. Any help would be appreciated.

This is my (now working) code:

    public void render(SpriteBatch sb) {     Vector2 temp = new Vector2();     float angle = temp.set(entityManager.getPlayer().pos).sub(pos).angle();     TextureRegion region = new TextureRegion(texture);     sb.draw(region, pos.x, pos.y, 0, 0, texture.getWidth(), texture.getHeight(), 1.0f, 1.0f,angle+90); } 

The enemy spaceships rotate, but they dont always face the player:

回答1:

The @dwn's answer is mathematically correct, but when you deal with LibGDX framework it's better to use native tools.

If you have positions of enemy and player storing in Vector2s then you may perform computations a bit convenient. For example, to determine angle between specific enemy and player:

Vector2 enemyPos; Vector2 playerPos; Vector2 temp;  float angle = temp                 .set(playerPos)                 .sub(enemyPos)                 .angle(); 

This will give you exactly what you want. Of course it's better to keep temp vector in somewhere in public space to use it in such numerous calculations. You better to check other convenient Vector2methods, it will seriously easy your life.

Good luck.

回答2:

I think this should work. Set..

v = centerPosOfShip - centerPosOfUFO 

Normalize...

v /= sqrt( v.x * v.x + v.y * v.y ) 

So now we can say v = [ cos(theta) sin(theta) ]; the rotation matrix is...

[ cos(theta)  -sin(theta) ] [ sin(theta)   cos(theta) ] 

So we can write in terms of v-components...

[ v.x  -v.y    centerPosOfUFO.x ][x] [ v.y   v.x    centerPosOfUFO.y ][y] [ 0     0      1                ][1] 

where [x y] is any point on the UFO relative to its center.

Hope that makes sense

来源：https://stackoverflow.com/questions/27671908/rotate-texture-in-function-of-player-position