Jump to content

What is the difference between "yaw balance" and "convergence" on a stereo vr stitch?


silencio615
 Share

Recommended Posts

They seem to do the same thing, and the tutorials don't explain the difference or when to use one or the other. Is there some documentation of the distinction?

 

How do horizontal balance and vertical balance play into this? Is there a simple order of which of these adjustments to do first and how to set them?

 

Link to comment
Share on other sites

Trying to figure this out on my own :-D I've always understood convergence to mean the distance at which adjacent images are stitched together. Yaw balance was confusing in the tutorials as it's adjusted in a similar manner, but it is very different as it is just the adjustment of left and right eyes and where they sit in relation to each other on the yaw axis - it has nothing to to with the stitch. Horizontal balance and yaw balance seem similar, still trying to figure out the distinction there.

 

I think the tutorials confused me on this one as they just gloss over some adjustments without explaining what they do. I still could be wrong on all this stuff, however.

Edited by silencio615
Link to comment
Share on other sites

Hi Silencio, 

    Many parameters are explained in the manual. Some parameters were experimental and we found they are not too useful, however we kept them just in case... These are two parameters that are useful and were not documented (we will add this to the manual too):

   Yaw Balance: Applies a horizontal (yaw) balance, aka convergence, between left and right eye AFTER the image is stitched. Yaw balance is applied as the last step, so using it will not influence in any way the optical flow stitching. Use this parameter when you see the stitch is fine, only the convergence is not at infinity, where it should normally be. 

   Roll Balance: This parameter only makes sense for cameras using coaxial pairs of lens heading in the same direction, like the Vuze, or some experimental rigs. The parameter offsets the Roll of all left eye cameras in one direction, while offsetting the roll of right eye in the opposite direction. Why: When importing a stitch from PTGui of APG, these stitchers both tend to get cheated by the fact that floor is usually much nearer than the sky above. Stitchers try to compensate this by tilting the cameras slightly downwards to all converge at the near feet of camera. However, for lens couples, the same phenomena will also roll slightly camera couples, each of the pair in opposite direction. Just as you use the "Vertical Balance" to compensate the near floor effect, use the Roll Balance to compensate the near floor effect. Remember that the  roll balance parameter only makes sense for coaxial lens couples based rigs. 

Link to comment
Share on other sites

Regarding the Convergence: This actually increases/decreases all lens focal length by certain percentage. +1 in convergence means increasing focal lenght of all cameras by 1%. 

When is this useful: The cameras are calibrated for objects at certain distance, ideally at infinity. However, if you are in a closed space, like a room, then the best first step to align the patches can be to decrease all the focal lengths. Why: The optical flow works by bending the images together where they do not match at the stitch. However, less bending needed, better the Optical Flow works, as it has less opportunities to get tit wrong. So, try to get the cameras aligned best you can before switching the Optical Flow on. 

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.