以45度角射击子弹

Question

I am trying to shoot a bullet at a 45 degree angle. However, it keeps shooting straight.

float armCos = (float)Math.Cos(0.0f - MathHelper.PiOver2);
float armSin = (float)Math.Sin(0.0f - MathHelper.PiOver2);

bullet.position = new Vector2(
                        arm.position.X + 42 * armCos,
                        arm.position.Y + 42 * armSin);

Answer 1

You can use this function that returns vector. Use is on your init bullet function and store into some variable and use it to update your bullet position.

public static Vector2 Vector2FromAngle(double angle, bool normalize = true)
{
    Vector2 vector = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle));
    if (vector != Vector2.Zero && normalize)
        vector.Normalize();
    return vector;
}