Description
Quaternion order is scalar-first [w,x,y,z], Hamilton product and right-handed active rotations; measure shortest rotation separation through absolute unit dot product, treating q and -q as identical.
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; measure shortest rotation separation through absolute unit dot product, treating q and -q as identical.
When to use this tool
Use this tool to measure shortest rotation separation through absolute unit dot product, treating q and -q as identical.
How to use the tool and how it works
- Enter left, right using the field definitions below.
- Run the operation. Correct input errors before interpreting an output.
- Read result.radians. Use the ordering, boundary rules and absence conditions described below.
Require unit endpoints and return twice arccos of their clamped absolute dot product.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| left | Left quaternion in [w, x, y, z] order. | Dense list of at most 128 finite numbers; integer/shape constraints above also apply. |
| right | Right quaternion in [w, x, y, z] order. | Dense list of at most 128 finite numbers; integer/shape constraints above also apply. |
| Output field | Interpretation |
|---|---|
| result | Object containing the named fields below. |
| result.radians | Rotation angle or shorter rotation separation, in radians. |
{
"input": {
"left": [
1,
0,
0,
0
],
"right": [
0,
1,
0,
0
]
},
"output": {
"result": {
"radians": 3.141592653589793
}
}
}Limitations and assumptions
- The result is the shorter rotation separation in radians from zero through pi; opposite quaternion signs are equivalent.
- 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
Similar or alternative tools
- Axis Angle to Unit Quaternion Record
Quaternion order is scalar-first [w,x,y,z], Hamilton product and right-handed active rotations; convert an explicit nonzero axis and angle to a unit quaternion; axis is normalized, radians are not silently clamped.
- Unit Quaternion Basis Vector Images
Quaternion order is scalar-first [w,x,y,z], Hamilton product and right-handed active rotations; return the three active basis-vector images as columns-as-vectors, not a transposed row-major matrix convention.