'Positioning UI or Camera relatively to each other (and screen border)

I'm struggling with this sort of Screen disposition. I want to position my Camera so that the world is positionned like in the image with the origin at bottom left. It's easy to set the orthographicSize of the camera as I know how many unit I want vertically. It is also easy to calculate the Y position of the camera as I just want it to be centered vertically. But I cannot find how to compute the X position of the camera to put the origin of the world in this position, no matter what the aspectRatio of the screen is.

It brings me two questions :

  1. How can I calculate the X position of the camera so that the origin of the world is always as the same distance from the screen left and bottom borders ?
  2. Instead of positioning the camera regarding the UI, should I use RenderMode Worldspace for the UI canvas. And if so, how could I manage responsiveness ?
unity3d


Solution 1:[1]

I don't understand the second question, but regarding positioning the Camera on the X axis so that the lower left corner is always at world 0 you could do the following:

var lowerLeftScreen = new Vector3(0, 0, 10);
var pos = transform.position;
var lowerLeftScreenPoint = Camera.main.ScreenToWorldPoint(lowerLeftScreen).x;
if (lowerLeftScreenPoint > 0)
{
    pos.x -= lowerLeftScreenPoint;
}
else
{
    pos.x += Mathf.Abs(lowerLeftScreenPoint);
}
transform.position = pos;
Debug.Log(Camera.main.ScreenToWorldPoint(lowerLeftScreen));

Not the nicest code, but gets the job done.
Also the Z component in the Vector does not really matter for our orthographic camera.

Sources

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Solution Source
Solution 1 Orca

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