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Add vector product to Euclidean3DSpace

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This commit is contained in:
Alexander Nozik 2023-03-10 12:01:08 +03:00
parent db61f71440
commit 4871baf0e5
3 changed files with 78 additions and 17 deletions
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2
gradle.properties
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@ -9,7 +9,7 @@ kotlin.native.ignoreDisabledTargets=true
org.gradle.configureondemand=true
org.gradle.jvmargs=-Xmx4096m
toolsVersion=0.14.2-kotlin-1.8.10
toolsVersion=0.14.3-kotlin-1.8.20-RC
org.gradle.parallel=true

47
kmath-geometry/src/commonMain/kotlin/space/kscience/kmath/geometry/Euclidean3DSpace.kt
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@ -78,8 +78,11 @@ public object Euclidean3DSpace : GeometrySpace<DoubleVector3D>, ScaleOperations<
}
}
public fun vector(x: Double, y: Double, z: Double): DoubleVector3D =
Vector3DImpl(x, y, z)
public fun vector(x: Number, y: Number, z: Number): DoubleVector3D =
Vector3DImpl(x.toDouble(), y.toDouble(), z.toDouble())
vector(x.toDouble(), y.toDouble(), z.toDouble())
override val zero: DoubleVector3D by lazy { vector(0.0, 0.0, 0.0) }
@ -100,6 +103,48 @@ public object Euclidean3DSpace : GeometrySpace<DoubleVector3D>, ScaleOperations<
override fun DoubleVector3D.dot(other: DoubleVector3D): Double =
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 if [rightBasis] is true and
* left-handed otherwise
*/
public fun vectorProduct(
first: DoubleVector3D,
second: DoubleVector3D,
rightBasis: Boolean = true,
): DoubleVector3D {
var x = 0.0
var y = 0.0
var z = 0.0
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 right basis
*/
public infix fun DoubleVector3D.cross(other: DoubleVector3D): Vector3D<Double> = vectorProduct(this, other)
public val xAxis: DoubleVector3D = vector(1.0, 0.0, 0.0)
public val yAxis: DoubleVector3D = vector(0.0, 1.0, 0.0)
public val zAxis: DoubleVector3D = vector(0.0, 0.0, 1.0)

46
kmath-geometry/src/commonTest/kotlin/space/kscience/kmath/geometry/Euclidean3DSpaceTest.kt
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@ -57,23 +57,39 @@ internal class Euclidean3DSpaceTest {
}
@Test
fun add() {
with(Euclidean3DSpace) {
assertVectorEquals(
vector(1.0, -2.0, 0.001),
vector(1.0, -2.0, 0.001) + zero
)
assertVectorEquals(
vector(8.0, -3.0, 3.001),
vector(1.0, 2.0, 3.0) + vector(7.0, -5.0, 0.001)
)
}
fun add() = with(Euclidean3DSpace) {
assertVectorEquals(
vector(1.0, -2.0, 0.001),
vector(1.0, -2.0, 0.001) + zero
)
assertVectorEquals(
vector(8.0, -3.0, 3.001),
vector(1.0, 2.0, 3.0) + vector(7.0, -5.0, 0.001)
)
}
@Test
fun multiply() {
with(Euclidean3DSpace) {
assertVectorEquals(vector(2.0, -4.0, 0.0), vector(1.0, -2.0, 0.0) * 2)
}
fun multiply() = with(Euclidean3DSpace) {
assertVectorEquals(vector(2.0, -4.0, 0.0), vector(1.0, -2.0, 0.0) * 2)
}
@Test
fun vectorProduct() = with(Euclidean3DSpace) {
assertVectorEquals(zAxis, vectorProduct(xAxis, yAxis))
assertVectorEquals(zAxis, xAxis cross yAxis)
assertVectorEquals(-zAxis, vectorProduct(yAxis, xAxis))
assertVectorEquals(zAxis, vectorProduct(yAxis, xAxis, rightBasis = false))
}
@Test
fun doubleVectorProduct() = with(Euclidean3DSpace) {
val a = vector(1, 2, -3)
val b = vector(-1, 0, 1)
val c = vector(4, 5, 6)
val res = a cross (b cross c)
val expected = b * (a dot c) - c * (a dot b)
assertVectorEquals(expected, res)
}
}