Oblique Frustrum on Multiple Cameras

Question

I need to create an oblique frustrum on 3 scene cameras. I'm using Unity's canned SetObliqueness function, which works fine for a single camera. For some reason, when I add additional cameras, the frustrum will only go oblique on the newest camera. If I deactivate a camera, the most recently added camera will return properly oblique, but adding back the deactivated camera removes the obliqueness. I've tried renaming variables and functions and using Camera.current vs. Camera.main but at most, I can only get one camera oblique. I really need to get this functioning properly. Anyone have any ideas?

Answer 1

Well, your method only works on the main camera. You have to change the method so it can work on a different camera.

You could create a seperate script which contains this:

 //ObliqueFrustum.cs
 using UnityEngine;
 
 public class ObliqueFrustum : MonoBehaviour
 {
     private Camera cam;
     public Vector2 offset;
     void Start()
     {
         cam = GetComponent<Camera>();
         SetMatrix(cam, offset);
     }
     public void SetObliqueness(float horizObl, float vertObl)
     {
         offset = new Vector2(horizObl, vertObl);
         SetMatrix(cam, offset);
     }
     
     public static void SetMatrix(Camera cam, Vector2 offset)
     {
         Matrix4x4 mat  = cam.projectionMatrix; 
         mat[0, 2] = offset.x;
         mat[1, 2] = offset.y;
         cam.projectionMatrix = mat;
     }
 }

Just attach this script to each camera object and set the offset in the inspector. If you want to change the obliquness later at runtime you can call "SetObliqueness()" on the appropriate instance of your script.

Maybe a bit more flexible would be:

 //ObliqueFrustum.cs
 using UnityEngine;
 
 public class ObliqueFrustum : MonoBehaviour
 {
     public Vector2 offset;
     void Start()
     {
         GetComponent<Camera>().SetObliqueProjection(offset)
     }
 }
 
 public static class CameraFrustumExtensions
 {
     // extension method of the Camera class, needs to be in a static class
     public static void SetObliqueProjection(this Camera cam, Vector2 offset)
     {
         Matrix4x4 mat  = cam.projectionMatrix; 
         mat[0, 2] = offset.x;
         mat[1, 2] = offset.y;
         cam.projectionMatrix = mat;
     }
     public static void SetObliqueProjection(this Camera cam, float horizObl, float vertObl)
     {
         SetObliqueProjection(cam, new Vector2(horizObl, vertObl));
     }
 }

This way you can simply call "SetObliqueProjection" on any camera reference. So you don't need to attach the "ObliqueFrustum" script to the camera as long as you reference the correct camera. For example:

 // some other manager script
 // ...
 public Camera cam1; // assigned in the inspector
 public Camera cam2;
 public Camera cam3;
 
 void Start()
 {
     // using the extension method we defined above.
     cam1.SetObliqueProjection(x1, y1);
     cam2.SetObliqueProjection(x2, y2);
     cam3.SetObliqueProjection(x3, y3);
 }

Oblique Frustrum on Multiple Cameras

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