[Fstarnb]

Type

• New feature (non-breaking dense-layout query). Related to Unsure about correctness of the implementation of IsContiguous #7363.

Motivation and Context

Tensor::IsContiguous() intentionally means C-contiguous, so a tensor with a different axis order can still occupy one gap-free, non-overlapping memory span while returning false. This adds a separate query for that layout without changing existing IsContiguous() behavior.

Checklist

• I have run python util/check_style.py --apply to apply Open3D code style.
• This PR changes Open3D behavior or adds new functionality.
  • Both C++ and Python API documentation are updated, including a Python usage example.
  • C++ and Python regression tests cover dense permutations, C-order layouts, negative strides, holes, overlap/broadcast, singleton dimensions, empty/scalar tensors, malformed metadata, and signed-span overflow.
• I will follow up and update the code if CI fails.
• For this fork PR, maintainers can edit the branch.

Description

Adds Tensor::IsDense() and Tensor.is_dense() to report non-overlapping tensors whose elements cover one contiguous span in any dimension order. Singleton strides are ignored; empty tensors and scalars are dense. Negative strides are checked by magnitude, with documentation warning that density alone does not make a forward memcpy safe. Spans outside Open3D's signed int64_t element/offset range are rejected.

Verification

Passed locally:

• A standalone C++17 harness calling the implementation in Tensor.h, including the issue layout, negative strides, empty/scalar, holes, overlap, and overflow cases.
• Syntax-only compilation of cpp/tests/core/Tensor.cpp with the generated Open3D compile flags.
• Python syntax compilation of python/test/core/test_core.py.
• Changed-line clang-format and YAPF checks, plus git diff --check.

The repository tests executable and Python runtime test were not run locally. The combined C++ test target begins by building Open3D's full VTK dependency chain, and the local build was stopped before reaching the test binary. Please use CI to validate the complete test matrix.

[update-docs]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[Fstarnb]

All GitHub Actions workflows for this PR currently show action_required, and no jobs have executed. The PR description documents the local test limitations, and Codacy passed. Could a maintainer approve the workflow runs when convenient so the full CI matrix can run?