Getting Position and Orientation (Rotation) of Light object with respect to camera

Unity Engine
,
1

Hello,

I’m new to Unity and C#, I wanted to ask for an environment where I have 1 light source, and multiple cameras (4) at different locations, how can I get the position & rotation (i.e. orientation) of the light source with respect to the different cameras.

I tried with
InverseTransformDirection &
InverseTransformPoint

I’ve written a script like this:

foreach(GameObject go in GameObject.FindGameObjectsWithTag("MainCamers"))
        {
            // Get the camera:
            Camera cam = go.GetComponent<Camera>();
            TransformMatrix = go.transform;
            // calculate transformation matrix... get light pos relative to camera
            // get light component
            _light = GetComponent<Light>();
            // get light position, orientation & intensity:
            _light_pos = _light.transform.position;
            RelativePos = TransformMatrix.InverseTransformPoint(_light_pos);
            _light_orient = _light.transform.rotation;
            RelativeOrient = TransformMatrix.InverseTransformDirection();
}

However, I’m still struggling to understand whether I’m understanding this problem / formulation correctly or not.
Any help would be highly appreciated.

2

What is it you are trying to do? Rotate the light to face the active camera? At the moment you setting its position and rotation multiple times.

3

Aaah I didn’t realise I was doing that :eyes:, I am doing a robotics project, so I just want the gameObject in my case the light’s position relative to the camera. So on the Unity environment I set the light position, though that’s in the 3D world coordinates, I want it’s position relative to the camera such that, x and y are local pixel coordinates and z is the depth (so still world).
And I want to extract this for each camera

So tldr; I want the light’s position & orientation to stay as it is, I just want to convert it’s position & orientation relative to the cameras.

4

Would this be right?
If I made the light a child of each of the camera object and then extracted it’s transform.localPosition?

foreach(GameObject go in GameObject.FindGameObjectsWithTag("MainCamers"))
        {
            // Get the camera:
            Camera cam = go.GetComponent<Camera>();
            // get light component
            _light = GetComponent<Light>();
            // make light the child of camera object; 
            _light.transform.parent = cam.transform;
            //_light is now the child of cam
            // get relative light position, orientation & intensity:
            _lightPos = _light.transform.localPosition;
            _lightOrient= _light.transform.localRotation;
}
5

You are still setting the variable multiple times. What do you mean by covert? What is it you want to do with the data?

6

erm… well I guess, convert is a poor choice of word, I just want the light position with respect to the cameras not as world position.
with the data, I just want to store it as a json file. I later want to plot / track the changes as the camera moves around the environment on a fixed trajectory.

7

If you want the difference between two vectors just subtract them. If you want multiple positions, store each vector in a list.

8

Yes, that’s what I’m aiming to do :slight_smile: thanks.
Though I just wanted to confirm that will the following;

_lightPos = _light.transform.localPosition;
_lightOrient= _light.transform.localRotation;

Actually give me what I want, the relative position of light to the camera?