fix(planar): map dynamic-volume flattened indices to their group-local slice

[sedghi]

Context

Follow-up to #2800. getVolumeImageIdIndexWorldPoint assumes a one-to-one imageId-to-k-slice mapping, but StreamingDynamicImageVolume flattens its imageIds across all dimension groups while dimensions[2] is the slice count of a single group. A referenced image (navigation) or an explicitly carried initial slice from any later dimension group therefore has a flattened index of at least dimensions[2], and the clamp sent every such image to the final slice instead of its group-local k.

Changes & Results

• Convert the flattened index through the volume's own flatImageIdIndexToImageIdIndex mapping (the k axis repeats per dimension group) before resolving the IJK world center. Duck-typed: static volumes have no such method and pass through unchanged, keeping fix(planar): anchor imageId-addressed slices at their exact IJK world center #2800's behavior identical for 3D volumes.
• Both consumers (view-reference navigation by referencedImageId / snapped plane points, and the mount-time initialImageIdIndex) route through this shared helper, so one conversion covers both.
• New test: a 3-group dynamic-volume mock asserts flattened index 14 (group 3, local slice 2) resolves to slice 2's world center rather than the raw-clamp result (final slice), and that first-group indices pass through unchanged.

Testing

• npx jest (packages/core): 31 suites, 535 passed.
• pnpm --filter @cornerstonejs/core run build:esm clean.

Checklist

PR

• My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• My code has been well-documented (function documentation, inline comments,
  etc.)

Summary by CodeRabbit

• Bug Fixes

  • Improved world-point calculations for dynamic 4D volumes with flattened image indexes.
  • Ensured slice positions are mapped to the correct dimension group instead of being incorrectly clamped.

• Tests

  • Added coverage for flattened dynamic-volume index mapping, including cross-group and first-group scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b867c6f3-44c8-44a1-87be-8ad4eeb2785b

📥 Commits

Reviewing files that changed from the base of the PR and between 6d2d80b and 024609c.

📒 Files selected for processing (2)

• packages/core/src/RenderingEngine/GenericViewport/Planar/planarSliceBasis.ts
• packages/core/test/planarSliceBasis.jest.js

---

📝 Walkthrough

Walkthrough

The planar slice world-point calculation now maps flattened dynamic-volume image indices to group-local slice indices before computing coordinates. A Jest test covers both remapped and unchanged indices.

Changes

Dynamic volume world-point mapping

Layer / File(s)	Summary
Map flattened indices to slice coordinates packages/core/src/RenderingEngine/GenericViewport/Planar/planarSliceBasis.ts, packages/core/test/planarSliceBasis.jest.js	The calculation optionally uses flatImageIdIndexToImageIdIndex, clamps the resulting local slice index, and tests remapped and pass-through indices.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• cornerstonejs/cornerstone3D#2800: Modifies the same world-point logic for planar slice center calculations.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise, descriptive, and accurately reflects the main change to dynamic-volume index mapping.
Description check	✅ Passed	The description follows the template well with clear Context, Changes & Results, Testing, and checklist details.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/planar-dynamic-volume-slice-index

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}