Differences

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--- stacker:docs:syntheticstereo [2023/03/18 17:48]
rjlittlefield Added sections "Retouching" and "Slabbing"
+++ stacker:docs:syntheticstereo [2023/06/18 17:33]
rjlittlefield [Retouching]
@@ Line 120: / Line 120: @@
 ===== Tips For Best Results =====
 The best shifts to use depend on your application and preferences.  For our test stacks, values of +-2% or +-3% often work well.
@@ Line 141: / Line 139: @@
 If you are on a Windows computer or have Windows emulation software, you should consider getting a copy of the free StereoPhoto Maker software (http://stereo.jpn.org/eng/stphmkr/).  It provides an excellent viewer that allows displaying a single image in various display formats, including crossed-eye, parallel viewing, red-cyan anaglyphs, and many other less common forms.  It also provides a variety of editing capabilities.  Cropping is especially handy, since this feature is not yet built into Zerene Stacker.
+When using StereoPhoto Maker, it is best to __not__ use any of its alignment features, other than shift left/right to adjust overall depth position with respect to the display surface.  All other sorts of alignment features, such as Adjust > "Auto alignment" are far more likely to introduce defects than to make any improvements.  This is because those features are designed to fix certain issues that are common in camera-based stereo but never occur in Zerene Stacker synthetic stereo.  In most cases StereoPhoto Maker will realize that there are no issues to fix, but in some cases it will mistakenly think that it sees a fixable problem, apply some "fix" like rolling the images, and mess things up in the process.
 ===== Retouching =====
-As a general rule, retouching of stereo images should be avoided, except to fix transparent foreground artifact as explained below under Slabbing.
+In most cases you cannot retouch shifted outputs from __un__shifted inputs because image features will not line up correctly.
-The reason for this restriction 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 key trick for retouching shifted images is to retouch shifted outputs from other outputs that were generated with the same shift.**
-It is almost impossible 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.
+You can use a targeted Stack Selected, or systematic batch slabbing, to generate the shifted outputs to use as source for retouching.
-So consider yourself warned: avoid retouching stereo images except to fix transparent foreground.
+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.
 ===== Slabbing =====
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   * subjectStackDepth = stack depth at the subject
   * viewAngle = viewing angle, measured as angular deviation from the usual straight-on view
+Recent versions of Zerene Stacker include a Stereo Shift Calculator, which automates the  required computations.
+Here is an example of its use, corresponding to the numbers shown below:
+{{:stacker:docs:syntheticstereo:image008.jpg}}
 Given these values, the calculation is straightforward:
@@ Line 255: / Line 274: @@
 Viewing angles that are off axis vertically use the same rules, substituting height for width and Y for X.  Note that this means the same angle will require different shift percents for X and Y, in proportion to the frame dimensions.
-Recent versions of Zerene Stacker include a Stereo Shift Calculator, which automates the above computations.
-Here is an example of its use, corresponding to the numbers shown above:
-{{:stacker:docs:syntheticstereo:image008.jpg}}
 ===== Other Resources =====