Scene view stretches camera frustum gizmo

Questions & Answers
1

Hi,

I am drawing my own camera frustums using Gizmos because I want camera frustums to always be visible, not just when I select the camera object.

The problem is that when I resize the ‘scene’ window the gizmo stretches as if it’s trying to match the aspect ratio of the scene view. The Unity camera frustum however doesn’t stretch like this.

Attached is my code and screenshots. Thanks!

using UnityEngine; 
using System.Collections;

[RequireComponent(typeof(Camera))]
public class ShowCameraFrustum : MonoBehaviour 
{
 void OnDrawGizmos()
 {
 // Top left
 Vector3 tlN = this.camera.ScreenToWorldPoint(new Vector3(Screen.width*0, Screen.height, this.camera.nearClipPlane));
 Vector3 tlF = this.camera.ScreenToWorldPoint(new Vector3(Screen.width*0, Screen.height, this.camera.farClipPlane));

 // Top right
 Vector3 trN = this.camera.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, this.camera.nearClipPlane));
 Vector3 trF = this.camera.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, this.camera.farClipPlane));
 
 // Bottom left
 Vector3 blN = this.camera.ScreenToWorldPoint(new Vector3(0.0f, 0.0f, this.camera.nearClipPlane));
 Vector3 blF = this.camera.ScreenToWorldPoint(new Vector3(0.0f, 0.0f, this.camera.farClipPlane));
 
 // Bottom right
 Vector3 brN = this.camera.ScreenToWorldPoint(new Vector3(Screen.width, 0.0f, this.camera.nearClipPlane));
 Vector3 brF = this.camera.ScreenToWorldPoint(new Vector3(Screen.width, 0.0f, this.camera.farClipPlane));
 
 Gizmos.color = Color.white;
 
 // Near
 Gizmos.DrawLine(tlN, trN);
 Gizmos.DrawLine(trN, brN);
 Gizmos.DrawLine(brN, blN);
 Gizmos.DrawLine(blN, tlN);
 
 // Far
 Gizmos.DrawLine(tlF, trF);
 Gizmos.DrawLine(trF, brF);
 Gizmos.DrawLine(brF, blF);
 Gizmos.DrawLine(blF, tlF);

 // Sides
 Gizmos.DrawLine(tlN, tlF);
 Gizmos.DrawLine(trN, trF);
 Gizmos.DrawLine(brN, brF);
 Gizmos.DrawLine(blN, blF);
 }
}

2198-frustum1.png
2198-frustum1.png723×318 28.6 KB

2199-frustum2.png

2

Don’t use Screen.width / .height. Use Camera.ViewportToWorldPoint with normalized coordinates instead (0.0 - 1.0).

Btw, i’m not sure if Unity will use the size of the scene view for all cameras, in this case, there’s not much you can do about that. If not, make sure you keep your game view at the same size. Each camera as an aspect ratio and it’s always calculated from the rendertarget.

You might want to set a fix aspect ratio for your camera.

3

UPDATE

It seems the the aspect ratio set in the ‘game’ view affects the camera frustum display in Unity. I can’t seem to find a way to get this aspect ratio though…

I found a fix that works:

float gameAspect = 1280.0f / 720.0f;  // hardcoded for now
float scale = gameAspect / camera.aspect;
tlN.x *= scale;
tlF.x *= scale;

…

So this scales the X component for all the points in the code above. This works well (in this case if you ‘game’ view is set to resolution 1280:720 or 16:9 aspect. It’s possible to set this resolution to ‘free’ or 4:3 which breaks it though, so I guess this is partial fix.

4

SOLVED

Using the code from here to get the size of the game viewport:
http://answers.unity3d.com/questions/179775/game-window-size-from-editor-window-in-editor-mode.html

Naturally as this is using reflection and undocumented ‘features’ it’s a bit of a hack but it’s good enough for me :slight_smile: Hope this little script is usesome to someone :slight_smile:

Here’s the final code:

using UnityEngine; 
using System.Collections;

[RequireComponent(typeof(Camera))]
public class ShowCameraFrustum : MonoBehaviour 
{
 public static Vector2 GetMainGameViewSize()
 {
     System.Type T = System.Type.GetType("UnityEditor.GameView,UnityEditor");
     System.Reflection.MethodInfo GetSizeOfMainGameView = T.GetMethod("GetSizeOfMainGameView",System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
     System.Object Res = GetSizeOfMainGameView.Invoke(null,null);
     return (Vector2)Res;
 }
 
 void OnDrawGizmos()
 {
 Camera cam = this.camera;
 
 // Top left
 Vector3 tlN = cam.ScreenToWorldPoint(new Vector3(Screen.width*0, Screen.height, cam.nearClipPlane));
 Vector3 tlF = cam.ScreenToWorldPoint(new Vector3(Screen.width*0, Screen.height, cam.farClipPlane));
 
 // Top right
 Vector3 trN = cam.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, cam.nearClipPlane));
 Vector3 trF = cam.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, cam.farClipPlane));
 
 // Bottom left
 Vector3 blN = cam.ScreenToWorldPoint(new Vector3(0.0f, 0.0f, cam.nearClipPlane));
 Vector3 blF = cam.ScreenToWorldPoint(new Vector3(0.0f, 0.0f, cam.farClipPlane));
 
 // Bottom right
 Vector3 brN = cam.ScreenToWorldPoint(new Vector3(Screen.width, 0.0f, cam.nearClipPlane));
 Vector3 brF = cam.ScreenToWorldPoint(new Vector3(Screen.width, 0.0f, cam.farClipPlane));
 
 // Scale for aspect ratio
 Vector2 gameViewsize = GetMainGameViewSize();
 float gameViewAspect = gameViewsize.x / gameViewsize.y;
 float s = gameViewAspect / cam.aspect; 
 tlN.x *= s;
 tlF.x *= s;
 trN.x *= s;
 trF.x *= s;
 blN.x *= s;
 blF.x *= s;
 brN.x *= s;
 brF.x *= s;
 
 Gizmos.color = Color.white;
 
 // Near
 Gizmos.DrawLine(tlN, trN);
 Gizmos.DrawLine(trN, brN);
 Gizmos.DrawLine(brN, blN);
 Gizmos.DrawLine(blN, tlN);
 
 // Far
 Gizmos.DrawLine(tlF, trF);
 Gizmos.DrawLine(trF, brF);
 Gizmos.DrawLine(brF, blF);
 Gizmos.DrawLine(blF, tlF);

 // Sides
 Gizmos.DrawLine(tlN, tlF); 
 Gizmos.DrawLine(trN, trF);
 Gizmos.DrawLine(brN, brF);
 Gizmos.DrawLine(blN, blF);
 }
}
5

put this on a camera script

void OnDrawGizmos() {
Gizmos.matrix = transform.localToWorldMatrix;
Gizmos.DrawFrustum( transform.position, camera.fieldOfView, camera.farClipPlane, camera.nearClipPlane, 1 );
}