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Unit Quaternion Short Arc NLERP

Quaternion order is scalar-first [w,x,y,z], Hamilton product and right-handed active rotations; perform shortest-sign normalized linear interpolation on the closed unit t domain; antipodal spelling is corrected, not interpolated through zero.

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Description

Quaternion order is scalar-first [w,x,y,z], Hamilton product and right-handed active rotations; perform shortest-sign normalized linear interpolation on the closed unit t domain; antipodal spelling is corrected, not interpolated through zero.

A quaternion has one scalar and three vector components. This family uses [w, x, y, z] unless a layout converter says otherwise. Unit quaternions can represent rotations, and q and −q describe the same rotation under this convention; component arithmetic and physical rotation interpretation are separate operations.

Quaternion order is scalar-first [w,x,y,z], Hamilton product and right-handed active rotations; perform shortest-sign normalized linear interpolation on the closed unit t domain; antipodal spelling is corrected, not interpolated through zero.

When to use this tool

Use this tool to perform shortest-sign normalized linear interpolation on the closed unit t domain; antipodal spelling is corrected, not interpolated through zero.

How to use the tool and how it works

  1. Enter left, right, t using the field definitions below.
  2. Run the operation. Correct input errors before interpreting an output.
  3. Read result.quaternion. Use the ordering, boundary rules and absence conditions described below.

Require unit endpoints and t from zero through one. Align signs using the dot product, linearly blend corresponding components, and normalize the result.1

Input fieldMeaning and unitsAccepted input
leftLeft quaternion in [w, x, y, z] order.Dense list of at most 128 finite numbers; integer/shape constraints above also apply.
rightRight quaternion in [w, x, y, z] order.Dense list of at most 128 finite numbers; integer/shape constraints above also apply.
tInterpolation fraction from 0 through 1.A finite number satisfying the operation’s stated comparisons.
Output fieldInterpretation
resultObject containing the named fields below.
result.quaternionFour result components in [w, x, y, z] order.
json
{
  "input": {
    "left": [
      1,
      0,
      0,
      0
    ],
    "right": [
      -1,
      0,
      0,
      0
    ],
    "t": 0.5
  },
  "output": {
    "result": {
      "quaternion": [
        1,
        0,
        0,
        0
      ]
    }
  }
}

Limitations and assumptions

  • Normalized linear interpolation generally does not travel at constant angular speed.
  • When an operation requires unit input, the fixed acceptance condition is |norm − 1| ≤ 1e−10. The norm audit instead uses its supplied tolerance. Angles use radians; vector units are preserved by a unit rotation. Floating-point roundoff is possible.
  • Every declared top-level input field is required and unexpected fields are rejected. Ordinary strings are limited to 8,192 UTF-16 code units and lists to 128 entries, with tighter operation-specific bounds where stated. JSON text has bounded nesting and node counts.
  • Numeric outputs must be finite and no larger in absolute magnitude than the safe-integer limit; operations returning exact large integers use decimal text. Positions are zero-based and spans end exclusively unless the operation explicitly states a different convention.

Alternative or Complementary methods

Confirm component layout, multiplication order and coordinate-frame convention before using another library’s records. Normalize only when appropriate, and distinguish component-space tolerances from angular tolerances.

References

  1. Tool behavior and example: Unit Quaternion Short Arc NLERP — tool.io

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