Fitting an ortographic cameras size to capture a 2D plane (aka image)

Hey there,

I'm working on a little project where the player can draw/write a line renderer on a plane. All of this is working fine. Now I want a function that saves an actual image (*.png) of that plane. For that I place an ortographic camera on it, that generates a RenderTexture. This RenderTexture is then used to calculate it's bytes to a png file.

Here is the code for the camera, if someone is interested:

Code (CSharp):

1. public class ScreenshotTool : MonoBehaviour
2.     {
3.         private int i;
4.         private Camera cam;
5.  
6.         private void Start()
7.         {
8.             cam = GetComponent<Camera>();
9.             cam.enabled = false;
10.         }
11.  
12.         public void CaptureImageOfTarget(Transform target, int resWidth, int resHeight)
13.         {        
14.             cam.orthographicSize = target.localScale.x / 11.111f;
15.             transform.rotation = target.rotation;
16.             transform.position = target.position + transform.forward * -0.1f;
17.  
18.             RenderTexture rt = new RenderTexture(resWidth, resHeight, 24);
19.             cam.targetTexture = rt;
20.             Texture2D screenShot = new Texture2D(resWidth, resHeight, TextureFormat.RGB24, false);
21.             cam.Render();
22.             RenderTexture.active = rt;
23.             screenShot.ReadPixels(new Rect(0, 0, resWidth, resHeight), 0, 0);
24.             cam.targetTexture = null;
25.             RenderTexture.active = null; // JC: added to avoid errors
26.             Destroy(rt);
27.             byte[] bytes = screenShot.EncodeToPNG();
28.             i++;
29.             string filename = target.name + "_Screenshot_" + i;
30.             File.WriteAllBytes(Path.Combine(Application.persistentDataPath, filename + ".png"), bytes);
31.             cam.enabled = false;
32.         }
33.     }

This line...

Code (CSharp):

1.             cam.orthographicSize = target.localScale.x / 11.111f;

... is just a placeholder that sort of works for my images that acually have a resolutuion I can calculate. But my goal is to fit the orthographicSize to a value, that fits my plane in worldSpace. So if my plane is 5x5 units, the frustum of the camera should wrap around the 5x5 units.

Could not really find a solution for that, yet.

 

You can use overlay canvas for your render texture instead of camere, there's handy pixels per unit option

 

Found a solution:

Code (CSharp):

1.   private float GetHeight(Canvas canvas)
2.         {
3.             Vector3[] v = new Vector3[4];
4.             canvas.GetComponent<RectTransform>().GetWorldCorners(v);
5.  
6.             return Vector3.Distance(v[0], v[1]) / 2;
7.         }
8.  

I'm using this method to get my orthographicSize. It gets the hight of my target canvas in world space. Don't need the width, because of the aspect ratio that comes from the resolution