How to make a flat world-aligned plane that fits the camera frustum?

What a mouthful!

I'm trying to follow the Projected Grid paper, and i'm having trouble getting my head around the right matrix math to get this to happen:

I'd appreciate any tips

 

You could do a ray from the screen 0,0 and screen.width, screen.height and get 4 Plane.Raycast's from that to get your info. The plane would be whatever your world is.

Are you wanting it like your image?

http://unity3d.com/support/documentation/ScriptReference/Plane.Raycast.html
http://unity3d.com/support/documentation/ScriptReference/Camera.ScreenPointToRay.html

If I am guessing correctly, you want to then create some geometry to show your plane. Create it at world center and make the 4 vertices those ray hits.

 

You might find camera.ViewportToWorldPoint useful here. The viewport point <0.5, 0.5, distance> is converted to the centre of the camera at the specified distance, so you can use this to position your plane. It is easiest if you can use a plane that extends in the local X and Y directions because you can then simply copy the camera's transform.rotation to the plane object to get it correctly oriented. As for the size of the frustum, the height at a specified distance is given by:-

Code (csharp):

1. var height = 2.0 * Mathf.Tan(camera.fieldOfView * Mathf.Deg2Rad * 0.5) * distance;

You can then multiply the height by the camera's aspect ratio to get the width of the frustum at the same distance.

 

Thanks for the responses. I shall try them out tonight!