   artoolkit and camera math
  Hy.Sorry for my english.I have created a project that display a plane with the texture that is grabbed from webcam via opencv.Every frame this texture is adjourned.Then i use marker tracking for detect the marker and get the modelviewmatrix every frame.After i have try to position a simple 3dobject on the marker.The modelviewmatrix return a rotation that work and a translation .My problem is the translation , in particulary the z translation.i read this excellent post:http://www.ogre3d.org/forums/viewtopic.php?f=5&t=22584&start=0.but i'm not understand at all.i see that can be a camera problem , im understand this:camera---------------object----------------->plane with grabbed camerahaw i can set and interpretate the camera and the plane.I'm not must move the plane , right ?then how convert the modelview matrix values for fitting it in this solution for simulate the back and away of the marker.Thansk.   
  How i can calculate the aspect ratio?For ex:at 20cm of the plane 8cm in the world are equal to near 6cm on the monitor, I can do this egualiance?But if i resize the viewport all is different , i can calculate the aspect ratio on the event onresize?but how?   