Le 26/11/2020 à 11:14, Antonio F.G. via groups.io a écrit :

I have played a little with 3Denlive, and followed the discussion on the 3D Spider-Man.
I am not fully on grips of the application but I feel it is extremely interesting to produce videos out of a sequence of stereo images, including zoom-in/out effects, and overlaying two or more stereo images.
In my opinion 3Denlive as a video editor would work best if the input SBS images are already well aligned for the main angular parameters (visual axis rotation, h-perspective, v-perspective, and nominal focus correction). The only alignment parameter that makes sense for zooming in-out is the h-disparity (displacement in the X direction).
As an example of this take one stereo image that has a 3.3% horizontal disparity. If we make a video sequence that ends in 5x zoom-in, the disparity would become 16.5% which is obviously too much. This is were it makes sense to displace in the X direction trying to reduce the disparity in the zoomed-in area, or possibly masking some area of the image that creates excessive disparity.

Exactly !

As shown in this tutorial about how to use keyframes, you can control all alignment and placement/zoom parameters to make them adapted at each time position of the video.

http://3denlive.com/doc/EN/KeyframedAnimation.php

You are speaking about horizontal disparity. But, on some stereos, you may have a well-aligned whole image having some local deformations. When zooming on these details, you may need to completely re-align the zoomed sub-part. This is here where the "Automatic alignment" button takes a great part of its interest!

For example, in the Spider-Man case, you may have a well-align whole video, but it's very hard to get it properly with a well-aligned Spider-Man (in fact, the background seems to be a simple flat wall-paper!). You would certainly like to have a better alignment on it when zooming.

In the tutorial, see the first screen copy point 7, and third screen copy point 3 and 4.

Your explanations may be a bit confusing because there are two X tuning:

- the horizontal stereo shift in the Alignment configuration

- the horizontal position in the Placement configuration

In the same idea, there are two parameters that may change the size aspect:

- the horizontal and vertical adaptation in the Alignment configuration

- the zoom factor in the Placement configuration

;-)