Add Gram-Schmidt orthonormalize() to Matrix3 and Matrix4

[Renanse]

What

Adds orthonormalize(store) / orthonormalizeLocal() to both Matrix3 and Matrix4, using the Gram-Schmidt process.

• Matrix3 — orthonormalizes its rows, matching the row-based isOrthonormal() check, so a cleaned matrix is guaranteed to pass it.
• Matrix4 — cleans only the upper-left 3×3 rotational block, copying the translation column (m03/m13/m23) and bottom row (m30–m33) through unchanged. This is the rendering-useful operation and matches how the Collada path decomposes a homogeneous matrix into rotation + translation.

In both, the first row's direction is preserved exactly; the remaining rows are made orthogonal to it (and each other) and unit length. A rank-deficient block throws ArithmeticException, mirroring invert()'s contract. Both variants are store-safe when the source is passed as the store.

Why

Rotation matrices from external tools — notably Autodesk FBX→Collada / OpenCollada exporters — frequently carry enough floating-point rounding error to fail isOrthonormal(), which trips the long-standing "supplied transform with non-rotational matrices. May have unexpected results." warning flood on skeletal import and degrades the rotation extracted downstream. This adds the math primitive needed to clean those matrices up. Closes the math half of #32.

Note on the Matrix4 contract

Matrix4.isOrthonormal() tests the full 4×4 as a 4D orthonormal matrix, which is only ever true for a translation-free rotation. So Matrix4.orthonormalize() does not make isOrthonormal() return true on a matrix carrying translation — nor should it. Its contract is the 3×3 block (spelled out in the javadoc; the test asserts result.toMatrix3(null).isOrthonormal()).

Scope

Pure math addition — no existing call sites changed. Wiring this into the Collada importer (behind an opt-in flag) is deliberately left for a follow-up so this stays low-risk and reviewable on its own.

Tests

TestMatrix3 / TestMatrix4 each gain testOrthonormalize + testBadOrthonormalize: a skewed near-rotation matrix becomes orthonormal; translation column / bottom row verified preserved (Matrix4); a pure rotation round-trips unchanged; store and in-place variants covered; rank-deficient input throws. Full ardor3d-math suite green (241 tests, 0 failures).

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 46d65688-af10-45d3-b4bd-1b2bc0260996

📥 Commits

Reviewing files that changed from the base of the PR and between 3edc60c and b43f6e1.

📒 Files selected for processing (4)

• ardor3d-math/src/main/java/com/ardor3d/math/Matrix3.java
• ardor3d-math/src/main/java/com/ardor3d/math/Matrix4.java
• ardor3d-math/src/test/java/com/ardor3d/math/TestMatrix3.java
• ardor3d-math/src/test/java/com/ardor3d/math/TestMatrix4.java

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch matrix-orthonormalize

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