[servantftransperfect]

Description

Bug fixes in the expanding SfM pipeline (sfmExpanding) and the Ceres bundle adjustment. Each commit is one self-contained fix and can be reviewed on its own.

Bundle adjustment

• Loss function ownership — the Ceres problem now owns the loss functions. The shared Huber loss is created lazily per problem, and weighted observations get their own ScaledLoss. CeresOptions stores the Huber threshold instead of a loss object.

Local bundle adjustment strategy

• Landmark states restored on each LBA build — a landmark ignored by a previous local bundle could stay ignored for good.
• LBA distances stored by pose id — rig views sharing a pose keep the smallest distance.
• Exact cocardinalities — the number of landmarks shared by each pair of views was only computed when a view was first added, and from tracks rather than from the current observations. It is now updated incrementally from the landmarks that changed, at a cost linear in the number of observations.
• Reference pose of mesh-based landmarks — a landmark whose reference pose was ignored by the local strategy could stay active, and the bundle adjustment then threw std::out_of_range.
• Choice of local strategy — the local strategy is now used whenever an LBA policy is set (and the scene is large enough). If the policy cannot be built, it falls back to a full bundle.

Scene cleanup

• Rig views get their own pose id when their rig pose is removed — before, they kept sharing the pose id while being flagged as independent.
• eraseUnstablePosesAndObservations loops again when observations are removed — the result of the observation filter was overwritten by the landmark filter.

Expansion

• Failed re-triangulation removes the old landmark — before, a track that could not be re-triangulated kept its previous landmark.
• The expansion stops when a chunk fails — ExpansionChunk::process now returns EChunkResult (success / skipped / error). Before, a failed bundle left an unrefined scene and the expansion could still succeed. sfmExpanding still exits with a failure, but first saves the partial scene to the output, so the work can be resumed.
• lockAllIntrinsics is honored — the option was parsed but never used. All intrinsics are now locked, so they stay constant in the bundle and do not link every view in the connexity graph.

Behavior changes for users

• With lockAllIntrinsics, the lock flag is now saved in the output sfmData.
• When a chunk fails, sfmExpanding fails instead of finishing with an unrefined scene. The partial scene is still written to the output file.

Tests

New sfm_lbaPolicyConnexity test:

• ConnexityGraph_incrementalUpdate: reuses one graph across builds while landmarks are added, modified and removed, and compares it with a new graph.
• LbaPolicyConnexity_ignoredReferencePose: a landmark whose reference pose is ignored must be ignored as well.

Both tests fail when their fix is reverted.

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