From looking at your Mocha screen shot, it seems to me that the areas that are good to track: Windows, the bushes on either side of steps (try to include a little edge of steps).
Areas that are not so good to track: columns (not much texture), the shape on top left is very large and should focus more on the window and edge of house. The one on the right does not look very planar.
Generally, try to focus your areas on textures that all feel part of the same flat plane. The shape on the right includes a person in the foreground and trees at different depths. depending on camera motion, this would most likely be a bad track area.
to answer questions:
- Does this seem like a sufficient number of tracks? Having trouble finding areas to track as the dancers move all around the lead singer walking with the camera, occluding/interrupting what could have decent consistent track regions.
You need to avoid the dancers and focus the tracker in the flat background planes. Sometimes it helps to stop the track and move the shape to avoid a FG and then pick it back up. As long as you move the shape to an area that moves relative to the that tracked plane, it can be good.
- Because the camera was handheld with no Z-axis preservation, and the lead singer holding the camera also turns three corners, yaw orientation changes quite a bit. The horizon moves on all three axis quite a lot throughout the video. Is it worth creating keyframed Horizon Orientation points at different frames in time in the video to accommodate for the widely varied camera movement in different scene areas? Current tests on the footage seem to show that setting a single Horizon Orientation keyframe isn’t solving across the entire video
Yes - I would break up the shot with many overlapping track areas and then keyframe the reorient side (yellow) in that module.
a. is there any relationship between how many track regions are required for stabilizing an equirect and how jittery the footage is?
Not necessarily. Generally the less tracked regions the better. But for long complex moves, you do need to track multiple areas that overlap.
b. Does the stabilization process reduce sharpness due to translating/rescaling content?
Stabilization is a render/filtering process, but should not reduce sharpness too much. If you have to resort to multi-passes of stabilization, certainly you will see loss. Use BCC VR Sharpo to compensate?
Q1: is Reorientation popping a possible issue when a moving object enters a tracked area?
Yes absolutely. The reorientation will only be as good as your tracks. If you view the Surface of each track, look to see if the blue box jumps. This will point to bad tracks for each layer.
Q2: Do some areas lend themselves better for tracking (high contrast? vertical or horizontal lines? crisp detail?). Generally, texture is what you want. Vertical & horizontal lines are not always great textures. This is why the columns might not track well, as there is not much texture. In your image the windows, the bushes seem to look good. Sometimes trees can give you good tracks but in 360 with a lot of motion might have too much depth. Again think about textures that move together… textures at different dephs and move at different speeds are the areas to avoid.
Hope some of this helps