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I want to perform object placement based on parent object position.

For example, I have chest and head object. I want when I rotate chest object then as per chest rotation head object also rotate and transform.

For this thing to achieve I did following stuff but I don't achieve desire effect and can't able to understand what was I doing?

private void addRectangle(float angle) {

    Rectangle baseRectangle = new Rectangle(300f, 300f, 100f, 200f);
    baseRectangle.setRotationCenter(0f, 0f);
    // red base rectangle
    baseRectangle.setColor(1f, 0f, 0f);

    float tAngle = MathUtils.atan2(-200, 100f);
    float dist = FloatMath.sqrt(50 * 50 + 50 * 50);

    float pX = baseRectangle.getX()
            + FloatMath.cos(MathUtils.degToRad(baseRectangle.getRotation())
                    + tAngle) * dist;
    float pY = baseRectangle.getY()
            + FloatMath.sin(MathUtils.degToRad(baseRectangle.getRotation())
                    + tAngle) * dist;

    Rectangle childRectangle = new Rectangle(pX, pY, 50f, 50f);
    childRectangle.setRotationCenter(0f, 0f);
    // green child rectangle
    childRectangle.setColor(0f, 1f, 0f);


As function argument I provide desire angle on which both the object needs to be rotated. Someone please help me to get out from this problem.

share|improve this question
Here I want to know how object get placed based on other object angle and position. – Siddharth Apr 15 '13 at 3:37
up vote 0 down vote accepted

your angle and distance formula wrong. in your child position you get angle and dist that i define below code.

private void addRectangle(float angle) {
    float centerX, centerY;
    Rectangle baseRectangle = new Rectangle(300f, 300f, 200, 100f);
    centerX = baseRectangle.getX() + baseRectangle.getWidth() / 2;
    centerY = baseRectangle.getY() + baseRectangle.getHeight() / 2;
    baseRectangle.setColor(1f, 0f, 0f);
    float tAngle = -0.2f;
    float dist = 128f;
    float pX = centerX + FloatMath.cos(MathUtils.degToRad(angle) + tAngle)
            * dist;
    float pY = centerY + FloatMath.sin(MathUtils.degToRad(angle) + tAngle)
            * dist;
    Rectangle childRectangle = new Rectangle(pX, pY, 50f, 50f);
    childRectangle.setRotationCenter(0, 0);
    childRectangle.setColor(0f, 1f, 0f);
share|improve this answer
Thanks a lot for your help. It works completely. – Siddharth Apr 15 '13 at 16:42
This thing create another problem for me. In the above code you change the rotation center of child object so when I attach body to this object creates abnormal behavior. Because of different rotation point of child object and its body. So what to do in this situation? – Siddharth Apr 17 '13 at 4:34
if your child not movement after attaching parent and child then after attachChild change your rotation center of your child. or give me some code to identify wht a pro ? – Divyang Metalia Apr 17 '13 at 7:13
Basically I understand from your statement is that first I have to create object with corner rotation center at that time my object body was static and then change rotation center to its normal position when I need dynamic body. I tried this thing in same code only. I attach bodies in the above rectangles and get this problem. This thing I will check and reply you. Am I understand any wrong thing then please suggest. Thanks. – Siddharth Apr 18 '13 at 2:40
you can create body after attachChild or change rotation center. – Divyang Metalia Apr 18 '13 at 10:22

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