Moderators: Chris S., Pau, Beatsy, rjlittlefield, ChrisR
I hope this helps, but I expect there will still be issues that are unclear or confusing. Please ask about those.Retouching
In most cases you cannot retouch shifted outputs from unshifted inputs because image features will not line up correctly.
So, the key trick for retouching shifted images is to retouch shifted outputs from other outputs that were generated with the same shift.
You can use a targeted Stack Selected, or systematic batch slabbing, to generate the shifted outputs to use as source for retouching.
As a general rule, we recommend that you avoid retouching of stereo images, except to fix transparent foreground artifact. The reason for this recommendation is that any inconsistency between the two images will be glaringly obvious when viewed as a stereo pair. At the least, mismatching areas will call the viewer's attention by appearing to “flash”. At worst, if the retouching process has resulted in horizontal shifts of any patch, then in the stereo view that patch will be seen as pulled forward or pushed backward, so the apparent geometry will have been changed.
It is extremely difficult to avoid such inconsistencies when retouching each image independently, except for the special case of fixing transparent foreground artifact by retouching from Stack Selected of the foreground regions.
As a result, it often takes much more time and trouble to retouch a stereo pair than it does to retouch a single image to the same level of residual artifact.
So consider yourself warned: avoid retouching stereo images except to fix transparent foreground.
As an alternative, consider presenting your results in two forms: a retouched single image that is free of artifact but whose geometry may be unclear, combined with a stereo pair that clearly shows the geometry but may suffer from various artifacts.
Now, if you do want to proceed with retouching, then start by considering the situation.
If the artifacts to be removed are isolated to just one or a few areas, then the simplest and most efficient approach is to do targeted Stack Selected that covers just the troublesome areas. That will produce shifted outputs that do not show the transparent foreground problem, and you can retouch from the shifted Stack Selected outputs into the correspondingly shifted full stack outputs.
If the artifacts to be removed are widespread through the stack depth, then it can be more efficient to generate a large set of shifted Stack Selected outputs by using batch slabbing, as described below. However, again we note that even at its best this process takes a lot of time and trouble to do well, so we do not recommend retouching stereo pairs or multi-frame animations that have widespread artifacts.
Hello Pau,
It varies depending on the subject and how critical the viewer is. I have seen stereo images made from as few as 15 frames that looked OK on casual inspection. And I have seen stacks made from 50 frames that broke up into looking like obviously separated layers painted on cardboard when modestly zoomed in.
Thanks for this update Rik, it tracks with my experience. Systematic slabbing would be the 'right' way but requires perfection and consistency in how both images are retouched; short of two identical Zerene retouching instances on two side-by-side monitors doing each image of a stereo pair painstakingly matching, it often isn't satisfactory.rjlittlefield wrote: ↑Sun Jun 18, 2023 10:34 amI have just now rewritten the Retouching section of https://zerenesystems.com/cms/stacker/docs/syntheticstereo to read as follows:I hope this helps, but I expect there will still be issues that are unclear or confusing. Please ask about those.Retouching
In most cases you cannot retouch shifted outputs from unshifted inputs because image features will not line up correctly.
So, the key trick for retouching shifted images is to retouch shifted outputs from other outputs that were generated with the same shift.
You can use a targeted Stack Selected, or systematic batch slabbing, to generate the shifted outputs to use as source for retouching.
As a general rule, we recommend that you avoid retouching of stereo images, except to fix transparent foreground artifact. The reason for this recommendation is that any inconsistency between the two images will be glaringly obvious when viewed as a stereo pair. At the least, mismatching areas will call the viewer's attention by appearing to “flash”. At worst, if the retouching process has resulted in horizontal shifts of any patch, then in the stereo view that patch will be seen as pulled forward or pushed backward, so the apparent geometry will have been changed.
It is extremely difficult to avoid such inconsistencies when retouching each image independently, except for the special case of fixing transparent foreground artifact by retouching from Stack Selected of the foreground regions.
As a result, it often takes much more time and trouble to retouch a stereo pair than it does to retouch a single image to the same level of residual artifact.
So consider yourself warned: avoid retouching stereo images except to fix transparent foreground.
As an alternative, consider presenting your results in two forms: a retouched single image that is free of artifact but whose geometry may be unclear, combined with a stereo pair that clearly shows the geometry but may suffer from various artifacts.
Now, if you do want to proceed with retouching, then start by considering the situation.
If the artifacts to be removed are isolated to just one or a few areas, then the simplest and most efficient approach is to do targeted Stack Selected that covers just the troublesome areas. That will produce shifted outputs that do not show the transparent foreground problem, and you can retouch from the shifted Stack Selected outputs into the correspondingly shifted full stack outputs.
If the artifacts to be removed are widespread through the stack depth, then it can be more efficient to generate a large set of shifted Stack Selected outputs by using batch slabbing, as described below. However, again we note that even at its best this process takes a lot of time and trouble to do well, so we do not recommend retouching stereo pairs or multi-frame animations that have widespread artifacts.
--Rik
short of two identical Zerene retouching instances on two side-by-side monitors doing each image of a stereo pair painstakingly matching, it often isn't satisfactory.
True, the retouching cannot be exactly synchronous. However, it definitely can be painstakingly matched.WojTek wrote: ↑Thu Jun 29, 2023 6:19 amthey are not identical, they are rotated by an angle.short of two identical Zerene retouching instances on two side-by-side monitors doing each image of a stereo pair painstakingly matching, it often isn't satisfactory.
...
So a synchronous retouching is not really possible.
This is correct. Stereo 3D depends entirely on determining disparity by matching local textures. No texture, no disparity, no depth information.I have the impression that the background does not carry any 3D information as long as there are no shadows.
The center depth plane of the stack is in the same place in both images. All other depth planes are shifted left or right in proportion to their position in the stack, multiplied by the shift limits specified at Options > Preferences > Stereo/Rocking.I would be interested to know how I can add a shadow afterwards.
What is the relationship between the left image and the right one?
Imagine that the shadow is cast onto a plane that sits behind the subject, perpendicular to the optical axis. Then following the rule given above, that shadow should simply be shifted left or right in proportion to its depth behind the center of the stack. This situation is simple because the shape of the shadow is identical in both views.At what angle should the shadow finally be placed (left and right)?
