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Revert "Remove the choice of left-handed product. Refactor vectorProduct. Remove leviChivita function."

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This reverts commit 28b85b0f53.
This commit is contained in:
Alexander Nozik 2023-03-16 09:33:17 +03:00
parent 5625800fc9
commit cd2ade881a
1 changed files with 29 additions and 5 deletions
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34
kmath-geometry/src/commonMain/kotlin/space/kscience/kmath/geometry/Euclidean3DSpace.kt
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@ -103,21 +103,45 @@ public object Euclidean3DSpace : GeometrySpace<DoubleVector3D>, ScaleOperations<
override fun DoubleVector3D.dot(other: DoubleVector3D): Double = override fun DoubleVector3D.dot(other: DoubleVector3D): Double =
x * other.x + y * other.y + z * other.z x * other.x + y * other.y + z * other.z
private fun leviCivita(i: Int, j: Int, k: Int): Int = when {
// even permutation
i == 0 && j == 1 && k == 2 -> 1
i == 1 && j == 2 && k == 0 -> 1
i == 2 && j == 0 && k == 1 -> 1
// odd permutations
i == 2 && j == 1 && k == 0 -> -1
i == 0 && j == 2 && k == 1 -> -1
i == 1 && j == 0 && k == 2 -> -1
else -> 0
}
/** /**
* Compute vector product of [first] and [second]. The basis assumed to be right-handed. * Compute vector product of [first] and [second]. The basis assumed to be right-handed if [rightBasis] is true and
* left-handed otherwise
*/ */
public fun vectorProduct( public fun vectorProduct(
first: DoubleVector3D, first: DoubleVector3D,
second: DoubleVector3D, second: DoubleVector3D,
rightBasis: Boolean = true,
): DoubleVector3D { ): DoubleVector3D {
val (x1, y1, z1) = first var x = 0.0
val (x2, y2, z2) = second var y = 0.0
var z = 0.0
return vector(y1 * z2 - y2 * z2, z1 * x2 - z2 * x2, x1 * y2 - x2 * y2) for (j in (0..2)) {
for (k in (0..2)) {
x += leviCivita(0, j, k) * first[j] * second[k]
y += leviCivita(1, j, k) * first[j] * second[k]
z += leviCivita(2, j, k) * first[j] * second[k]
}
}
return vector(x, y, z) * (if (rightBasis) 1 else -1)
} }
/** /**
* Vector product with a right basis * Vector product with right basis
*/ */
public infix fun DoubleVector3D.cross(other: DoubleVector3D): Vector3D<Double> = vectorProduct(this, other) public infix fun DoubleVector3D.cross(other: DoubleVector3D): Vector3D<Double> = vectorProduct(this, other)