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Improved quaternion application #26456

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Oct 10, 2023
Merged

Improved quaternion application #26456

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23 changes: 11 additions & 12 deletions src/math/Vector3.js
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Original file line number Diff line number Diff line change
Expand Up @@ -251,21 +251,20 @@ class Vector3 {

applyQuaternion( q ) {

const x = this.x, y = this.y, z = this.z;
const qx = q.x, qy = q.y, qz = q.z, qw = q.w;
// Derived from https://raw.org/proof/vector-rotation-using-quaternions/

// calculate quat * vector

const ix = qw * x + qy * z - qz * y;
const iy = qw * y + qz * x - qx * z;
const iz = qw * z + qx * y - qy * x;
const iw = - qx * x - qy * y - qz * z;
const vx = this.x, vy = this.y, vz = this.z;
const qx = q.x, qy = q.y, qz = q.z, qw = q.w;

// calculate result * inverse quat
// t = 2q x v
const tx = 2 * ( qy * vz - qz * vy );
const ty = 2 * ( qz * vx - qx * vz );
const tz = 2 * ( qx * vy - qy * vx );

this.x = ix * qw + iw * - qx + iy * - qz - iz * - qy;
this.y = iy * qw + iw * - qy + iz * - qx - ix * - qz;
this.z = iz * qw + iw * - qz + ix * - qy - iy * - qx;
// v + w t + q x t
this.x = vx + qw * tx + qy * tz - qz * ty;
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this.y = vy + qw * ty + qz * tx - qx * tz;
this.z = vz + qw * tz + qx * ty - qy * tx;

return this;

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6 changes: 0 additions & 6 deletions test/unit/src/math/Vector3.tests.js
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Expand Up @@ -14,7 +14,6 @@ import {
x,
y,
z,
w,
eps
} from '../../utils/math-constants.js';

Expand Down Expand Up @@ -303,11 +302,6 @@ export default QUnit.module( 'Maths', () => {
assert.strictEqual( a.y, y, 'Identity rotation: check y' );
assert.strictEqual( a.z, z, 'Identity rotation: check z' );

a.applyQuaternion( new Quaternion( x, y, z, w ) );
assert.strictEqual( a.x, 108, 'Normal rotation: check x' );
assert.strictEqual( a.y, 162, 'Normal rotation: check y' );
assert.strictEqual( a.z, 216, 'Normal rotation: check z' );
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Why did you remove these unit tests?

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These unit tests are silly. They don't actually proof the correctness of the actual rotation. A non-normalized quaternion that is applied to the rotation algorithm can only serve as a kind of fingerprint for the formulas if the arbitrary numbers that get were put in, generate a certain output. As the formulas have changed, they don't provide the same output for non-normalized quaternions. All other unit-tests that work on actual versors work perfectly fine.


} );

QUnit.todo( 'project', ( assert ) => {
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