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--- stacker:docs:syntheticstereo [2020/07/12 22:01]
rjlittlefield [Other Resources] Add ref to synthetic vs true stereo comparison
+++ stacker:docs:syntheticstereo [2023/03/18 17:48]
rjlittlefield Added sections "Retouching" and "Slabbing"
@@ Line 140: / Line 140: @@
 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.
+===== Retouching =====
+As a general rule, retouching of stereo images should be avoided, except to fix transparent foreground artifact as explained below under Slabbing.
+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!
+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.
+So consider yourself warned: avoid retouching stereo images except to fix transparent foreground.
+===== Slabbing =====
+In general, "slabbing" is a two-step technique in which (1) sets of adjacent original source images are focus stacked to create "slab outputs", and then (2) the slab outputs are used as inputs to another stacking operation that puts the whole stack together. ( See [[https://zerenesystems.com/cms/stacker/docs/slabbing|Slabbing]] for a general discussion of slabbing.)
+Slabbing is a powerful way to simplify retouching, and it is particularly helpful for fixing "transparent foreground" artifact in stereo pairs.
+Used for this purpose, a good workflow for slabbing and stereo pair generation goes as follows.
+(One caution: this procedure should not only be read, but //followed//!  The procedure is long and complicated, and it is easy to go astray.)
+  - Launch Zerene Stacker.
+  - Load original source images.
+  - Determine two Shift X limits, one for each eye's viewpoint.
+  - Set general batch options:
+     * Menu select Options > Preferences.
+     * At Preferences > Alignment, be sure that appropriate options are selected.
+     * Set Preferences > Slabbing > "Stacking operation" to be PMax.
+     * Set Preferences > Slabbing > "How to save output images" to be "Keep only in project".
+     * Click OK to close Preferences dialog.
+     * Menu select Batch > Show Batch Dialog.
+     * Be sure the Queued Batches area is empty.  If any queued batches are present, then select and delete them.
+     * Close Dialog.
+  - Generate slab script for the __first eye's viewpoint__:
+     * Menu select Batch > Slabbing.  //(This will automatically open the Preferences dialog.)//
+     * Set Preferences > Stereo/Rocking to generate __one__ frame at the __first eye's__ Shift X limit. \\ //(Put a checkmark in the box to "Generate stereo pair or rocking sequence", \\ and put the same __negative__ number in both of the Shift X Limits fields.)//
+     * Set Preferences > Slab Saving > Template to be "First Eye Slab {outseq} {method}".
+     * Click OK to close dialog, generate batch script, and open the Batch Queue dialog.
+     * Close Dialog to close the Batch Queue dialog.
+  - Generate slab script for the __second eye's viewpoint__:
+     * Menu select Batch > Slabbing  //(This will automatically open the Preferences dialog.)//
+     * Set Preferences > Stereo/rocking to generate __one__ frame at the __second eye's__ Shift X limit. \\ //(Put a checkmark in the box to "Generate stereo pair or rocking sequence", \\ and put the same __positive__ number in both of the Shift X Limits fields.)//
+     * Set Preferences > Slab Saving > Template to be "Second Eye Slab {outseq} {method}".
+     * Click OK to close dialog, generate batch script, and open the Batch Queue dialog.
+     * Close Dialog
+  - Generate all slab outputs:
+     * Menu select Batch > Show Batch Dialog.
+     * Run All Batches.
+     * Close Dialog.
+  - Save slab outputs and load them as input files, __already aligned__:
+     * In the Output Images panel, select all slab outputs.
+     * File > Save Output Image(s), to any convenient location.
+     * At Options > Preferences > Preprocessing, be sure there is a checkmark on "__Add files to existing project as already aligned__".
+     * Add slab outputs to the Input Files Panel.
+  - Stack selected with __no added stereo shifts__, to generate each eye's view for the full stack:
+     * Menu select Options > Preferences.
+     * At Stereo/Rocking, be sure there is __no checkmark__ on "Generate stereo pair or rocking sequence".
+     * At Image Saving, set Template to be "First Eye ZS {method}".
+     * OK to close Preferences dialog.
+     * In the Input Images panel, select all First Eye images.
+     * Stack > Stack Selected (PMax)
+     * Menu select Options > Preferences
+     * At Image Saving, set Template to be "Second Eye ZS {method}".
+     * OK to close Preferences dialog.
+     * In the Input Images panel, select all Second Eye images.
+     * Stack > Stack Selected (PMax).
+The main products of this long and complicated procedure will be:
+  * Two output images, named "First eye ZS PMax" and "Second eye ZS PMax".
+  * A collection of slab images, named "First Eye Slab ..." and "Second Eye Slab ...". \\ These can be used to retouch the corresponding eye's main output image.
+Note that when retouching, it is a good idea to set Options > Preferences > Image Saving > Template to be either "First Eye..." or "Second Eye...", each time just before Edit > Commit.  This will help to keep straight which view is which.
+As already noted, the procedure is long and complicated, so there are lots of places to go astray.  Most missteps will be quickly obvious, but there is one type of error that can be quite mysterious.  That results from accidentally stacking with alignment and/or stereo shift added when they were not supposed to be.
+In particular, it is critical that:
+  * "Add files to existing project as already aligned" is selected, when the slab outputs are added back to the project as Input Files. If this is not done, then Stack Selected will try to re-align the stereo-shifted slabs to match the original source images, and that will generate nonsense output.
+  * There must be no checkmark on "Generate stereo pair or rocking sequence", when Stack Selected is run to combine the slabs to make full stack results.  If the checkmark is left in place at this stage, then the already-shifted slabs will be stereo-shifted again.  The resulting output will not be correct.  However, it may look reasonable at first glance, so the first hint of this error may be that when retouching is attempted, the slab images do not align properly with the full-stack composites.
+This documentation is rather new and no doubt can be improved.  Please report difficulties in using it, by sending email to support@zerenesystems.com .
 ===== Calculating Shift Based On Viewing Angle =====
@@ Line 166: / Line 254: @@
 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 =====