[Bf-docboard-svn] bf-manual: [9180] branches/blender-3.1-release/blender_docs/manual: Fix T97261: Incorrect page for 2D stabilization

[Alaska]

Revision: 9180
          https://developer.blender.org/rBM9180
Author:   Alaska
Date:     2022-04-12 02:13:22 +0200 (Tue, 12 Apr 2022)
Log Message:
-----------
Fix T97261: Incorrect page for 2D stabilization

Modified Paths:
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    branches/blender-3.1-release/blender_docs/manual/movie_clip/tracking/clip/sidebar/stabilization/workflow.rst

Added Paths:
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    branches/blender-3.1-release/blender_docs/manual/images/movie-clip_tracking_clip_sidebar_stabilization_workflow_irregular-tracks.png

Added: branches/blender-3.1-release/blender_docs/manual/images/movie-clip_tracking_clip_sidebar_stabilization_workflow_irregular-tracks.png
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Index: branches/blender-3.1-release/blender_docs/manual/images/movie-clip_tracking_clip_sidebar_stabilization_workflow_irregular-tracks.png
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--- branches/blender-3.1-release/blender_docs/manual/images/movie-clip_tracking_clip_sidebar_stabilization_workflow_irregular-tracks.png	2022-04-12 00:10:53 UTC (rev 9179)
+++ branches/blender-3.1-release/blender_docs/manual/images/movie-clip_tracking_clip_sidebar_stabilization_workflow_irregular-tracks.png	2022-04-12 00:13:22 UTC (rev 9180)

Property changes on: branches/blender-3.1-release/blender_docs/manual/images/movie-clip_tracking_clip_sidebar_stabilization_workflow_irregular-tracks.png
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Modified: branches/blender-3.1-release/blender_docs/manual/movie_clip/tracking/clip/sidebar/stabilization/workflow.rst
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--- branches/blender-3.1-release/blender_docs/manual/movie_clip/tracking/clip/sidebar/stabilization/workflow.rst	2022-04-12 00:10:53 UTC (rev 9179)
+++ branches/blender-3.1-release/blender_docs/manual/movie_clip/tracking/clip/sidebar/stabilization/workflow.rst	2022-04-12 00:13:22 UTC (rev 9180)
@@ -1,49 +1,147 @@
-
 ********
 Workflow
 ********
 
-Relative Shape Keys
-===================
+Depending on the original footage's properties, achieving good stabilization results might be simple and easy,
+or it might require some work, dedication and careful planning. This section covers some practical considerations
+to help improving the results.
 
-#. In *Object Mode*, add a new shape key via the *Shape Key* panel with the ``+`` button.
-#. "Basis" is the rest shape. "Key 1", "Key 2", etc. will be the new shapes.
-#. Switch to *Edit Mode*, select "Key 1" in the *Shape Key* panel.
-#. Deform mesh as you want (do not remove or add vertices).
-#. Select "Key 2", the mesh will be changed to the rest shape.
-#. Transform "Key 2" and keep going for other shape keys.
-#. Switch back to *Object Mode*.
-#. Set the *Value* for "Key 1", "Key 2", etc. to see the transformation between the shape keys.
 
-In the figure below, from left to right shows: "Basis", "Key 1", "Key 2"
-and mix ("Key 1" ``1.0`` and "Key 2" ``0.8``) shape keys in Object Mode.
+The Simple Case
+===============
 
-.. figure:: /images/animation_shape-keys_workflow_relative.png
+Whenever the camera is basically fixed, or at least "almost" stationary, and the footage is crisp and
+without motion blur, perfect stabilization is easy to achieve. This might be the case when a tripod was used,
+but wind or vibrations on the floor (e.g. on a stage) caused some minor shakes.
+Shoulder camera shots done by an experienced operator also frequently fall into this category.
 
-   Relative shape keys example.
+- Use as few points as possible. Start with a single point right on the main subject.
+- Track this single point as accurate as possible. Beware of movements and shape changes of the tracked feature.
+  Proceed in small increments (e.g. 50 frames), zoom in and readjust the target point manually when it drifts away.
+  Another option is to use a larger target area for tracking; since we're tracking only a single point,
+  the slower tracking speed might be acceptable.
+- After enabling the basic (location) stabilization, consider if you really need rotation stabilization.
+  Often, some minor, slow swinging movements are not really noticeable and do not warrant the additional working time
+  and quality loss caused by rotation and scale stabilization.
+- For rotation, start with one extra point, well spaced but preferably still attached to the main subject.
+- Consider to fix some slow residual motion by manually animating the "*Expected* \*" parameters,
+  before you even think of adding more tracking markers. Because doing so is often not worth the effort.
+- If you need to add more points, the most important goal is to achieve *symmetry.*
+  Place location tracking points symmetrically above and below the horizon.
+  Place rotation tracking points into diagonally opposed direction, always centered around the main focal area.
 
-For more practical examples, see
-:ref:`how to combine shape keys and drivers <shapekey-driver-example>`.
 
+Avoid Problematic Footage
+=========================
 
-Absolute Shape Keys
+The 2D stabilizer can not work miracles; some flaws simply can not be fixed satisfactory.
+Notorious issues are motion blur, rolling shutter, pumping autofocus and moving compression artifacts.
+Especially if you do succeed with basic stabilization, such image flaws become yet the more noticeable and annoying.
+When on set or on location, it might be tempting to "fix matters in postpro".
+Resist that deception, it rarely works out well.
+
+- Prefer a short exposure time to avoid motion blur.
+  While motion blur is good to render filmed movements more smooth and natural,
+  it seriously impedes the ability to track features precisely.
+  As a guideline, try to get at least to 1/250 s.
+- Prefer higher frame rates. The more *temporal resolution* the stabilizer has to work on, the better the results.
+  If you have the option to choose between progressive and interlaced modes, by all means use interlaced
+  and deinterlace the footage to the *doubled frame rate*. This can be done with
+  the `yadif <https://ffmpeg.org/ffmpeg-filters.html#yadif-1>`__ filter of FFmpeg: use the mode 1 (``send_field``).
+- Beware of the :term:`Rolling Shutter` effect. Avoid fast lateral movements.
+  If you can, prefer a camera which produces less rolling shutter.
+  Also, using a higher frame rate reduces the amount of rolling shutter; another reason to prefer
+  interlaced over progressive for the purpose at hand.
+- Switch off autofocus.
+  Better plan your movement beforehand, set a fixed focus and rely on depth of field through using a small aperture.
+  Pumping movements might not be so noticeable to the human observer, but the feature tracking tends to slide away
+  on defocused image elements; fixing this manually after the fact can cause a huge waste of time.
+- Increase the lighting level, at least use a higher sensitivity.
+  This helps to set a fast shutter speed plus a small aperture.
+  Better lighting and good exposure also help to reduce the impact of compression artifacts.
+  If you can, also select a codec with less data reduction, better color space, etc.
+  Inevitably, we're loosing some quality through the interpolation necessary for stabilization.
+  Plus we're loosing some quality due to color space conversion.
+
+
+Elaborate Movements
 ===================
 
-#. Add a sequence of shape keys as described above for relative shape keys.
-#. Uncheck the *Relative* checkbox.
-#. Click the *Reset Timing* button.
-#. Switch to *Object Mode*.
-#. Drag *Evaluation Time* to see how the shapes succeed one to the next.
+When the footage builds on elaborate intended movement of the camera,
+the process of stabilization becomes more involved --
+especially when there is a shift in the main area of interest within the shot.
+When working with many tracks and fine-grained animation,
+it is easy to get into a situation where additional manipulations actually decrease the quality,
+while it might be hard to spot and locate the root cause of problems.
+Recommendation is to proceed systematically, starting from the general outline down to tweaking of specific aspects.
 
-.. figure:: /images/animation_shape-keys_workflow_absolute.png
+#. Understand the nature of the movements in the shot, both the intended and the accidental.
+#. Track some relevant features for location.
+#. Establish the basic location stabilization.
+   This includes the decision, which feature to use for what segment of the shot.
+   Work with the track weights to get an overall consistent movement of the weight center,
+   in accordance with the inherent focus of the shot.
+#. Define the panning movements of the virtual camera (through animation of the *Expected Position* parameter).
+#. Add tracking for rotation and zoom stabilization.
+#. Fine-tuning pass:
 
-   Absolute shape keys workflow.
+   Break down the whole duration of the shot into logical segments to define the intended camera movement.
+   Then refine those segments incrementally step-by-step, until the overall result looks satisfactory...
 
-By adding a :doc:`driver </animation/drivers/index>` or
-setting :doc:`keyframes </animation/keyframes/introduction>`
-to *Evaluation Time* you can create an animation.
 
-.. seealso:: Shape Key Operators
+Animating Stabilization Parameters
+==================================
 
-   There are two modeling tools used to control shape keys and
-   are found in :ref:`Edit Mode <modeling-meshes-editing-vertices-shape-keys>`.
+Animating some parameters over duration of the shot is often necessary, at least to get the final touch,
+including control of the scale factor to hide the dancing black borders.
+Unfortunately there is a **known limitation** in the current version:
+it is not possible to open the generic animation editors (Graph editor and Dope Sheet)
+for animation data beyond the 3D scene. So, while it *is possible* to set keyframes *right within the UI controls*
+of the stabilizer (either through pressing the :kbd:`I` key or with the help of the context menu),
+it is not possible to manipulate the resulting curves graphically.
+The only way to readjust or remove a misguided keyframe is to locate
+the timeline to the very frame and then use the context menu of the animated UI control.
+(Hint: the color of the UI control changes when you have located at precisely the frame number of the keyframe.)
+
+
+Irregular Track Setup
+=====================
+
+It might not be possible to track a given feature over the whole duration of the shot.
+The feature might be blurred or obscured; it might even move out of sight entirely,
+due to deliberate camera movement.

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