Modify focal distance/image plane withour change FOV

Hi everybody,

I've a question about focal distance and FOV.

I'll try to explain my goal: I'm a researcher and in my lab we developed an immersive stereoscopic reality system, using an open source rendering engine. This engine let us do all the stuff we need in order to make our system work at its best, but the quality is quite awful. So we decide to switch to more advanced engine, like unity. Our system rely on a specific 3D visualization technique we patented, and it must modify the frustum of each virtual stereoscopic camera.

Back in unity, for now I'm able to modify the frustum of each camera by modifing the projection matrix, but I need to set the position of the image plane, aka its distance from the camera, aka the focal length. I must not use the tipical trick of changing the focal length by changing the FOV, cause in our system i need to set this two parameters indipendently.

So, back to my question:

There is any way to directly set the focal length?

In case of negative answer:

Do you know where is positioned in the world the image plane, aka its distance from the camera or from the near plane?

Thank you very much.

Matteo

 

Check my posts in this thread
http://forum.unity3d.com/threads/192409-Off-axis-projection-with-Unity
Not sure if this is what you need, its more of a 'looking through a window' projection thingy

Aren't focal length and FOV sort of the same thing?

 

Hi,

actually the "looking through a window" thing should work fine for me, but since i'm in a stereoscopic environment, I need to know where is the image plane, aka the glass of the window =) In not stereo system the lackness of this information is not a problem, but when it came to stereoscopic setup, where the two image for left/right eye must be matched together, this information is very important.

Focal Lenght and FOV are not the same thing, FL is the distance between the center of the camera and the image plane, and the FOV is the angle the describe how much is "wide" the view (more or less). They are not directly dependent because I may need to have a wider FOV with the same FL.

Maybe in Unity does not exist an Image Plane at all, it's just that I need to know in order to know how to work...

 

It seems Unity is using the near plane as image plane. I can see Unity is linked to OpenGL, and the OpenGL projection matrix is explained at http://www.scratchapixel.com/lesson...-matrix/opengl-perspective-projection-matrix/

Also, I printed camera.projectionMatrix from my Unity installation on Mac and was able to verify its values match the ones described at scratchapixel for OpenGL.