Add vector convenience functions.

indigo/indigo/src/main/scala/indigo/shared/datatypes/Vector2.scala

@@ -38,6 +38,8 @@ final case class Vector2(x: Double, y: Double) derives CanEqual:
   def invert: Vector2 =
     Vector2(-x, -y)
 
+  def `unary_-` : Vector2 = invert
+
   def translate(vec: Vector2): Vector2 =
     Vector2.add(this, vec)
 

indigo/indigo/src/main/scala/indigo/shared/datatypes/Vector3.scala

@@ -40,6 +40,8 @@ final case class Vector3(x: Double, y: Double, z: Double) derives CanEqual:
   def invert: Vector3 =
     Vector3(-x, -y, -z)
 
+  def `unary_-` : Vector3 = invert
+
   def translate(vec: Vector3): Vector3 =
     Vector3.add(this, vec)
 
@@ -85,6 +87,9 @@ final case class Vector3(x: Double, y: Double, z: Double) derives CanEqual:
   def dot(other: Vector3): Double =
     Vector3.dotProduct(this, other)
 
+  def cross(other: Vector3): Vector3 =
+    Vector3.crossProduct(this, other)
+
   def normalise: Vector3 =
     val magnitude = length
     if magnitude == 0 then Vector3.zero
@@ -126,6 +131,10 @@ object Vector3:
   val zero: Vector3 = Vector3(0d, 0d, 0d)
   val one: Vector3  = Vector3(1d, 1d, 1d)
 
+  val unitX: Vector3 = Vector3(1d, 0d, 0d)
+  val unitY: Vector3 = Vector3(0d, 1d, 0d)
+  val unitZ: Vector3 = Vector3(0d, 0d, 1d)
+
   def fromPoint(point: Point): Vector3 =
     Vector3(point.x.toDouble, point.y.toDouble, 0)
 
@@ -150,6 +159,13 @@ object Vector3:
   def dotProduct(vec1: Vector3, vec2: Vector3): Double =
     (vec1.x * vec2.x) + (vec1.y * vec2.y) + (vec1.z * vec2.z)
 
+  def crossProduct(vec1: Vector3, vec2: Vector3): Vector3 =
+    Vector3(
+      vec1.y * vec2.z - vec1.z * vec2.y,
+      vec1.z * vec2.x - vec1.x * vec2.z,
+      vec1.x * vec2.y - vec1.y * vec2.x
+    )
+
   def distance(v1: Vector3, v2: Vector3): Double =
     Math.sqrt(Math.abs(Math.pow(v2.x - v1.x, 2) + Math.pow(v2.y - v1.y, 2) + Math.pow(v2.z - v1.z, 2)))
 

indigo/indigo/src/main/scala/indigo/shared/datatypes/Vector4.scala

@@ -48,6 +48,8 @@ final case class Vector4(x: Double, y: Double, z: Double, w: Double) derives Can
   def invert: Vector4 =
     Vector4(-x, -y, -z, -w)
 
+  def `unary_-` : Vector4 = invert
+
   def translate(vec: Vector4): Vector4 =
     Vector4.add(this, vec)
 

indigo/indigo/src/test/scala/indigo/shared/datatypes/Vector3Tests.scala

@@ -135,6 +135,12 @@ class Vector3Tests extends munit.FunSuite {
     assert(clue(Vector3.mod(Vector3(-11), Vector3(-10))) ~== clue(Vector3(-1)))
   }
 
+  test("cross product") {
+    assertEquals(Vector3.unitX.cross(Vector3.unitY), Vector3.unitZ)
+    assertEquals(Vector3.unitY.cross(Vector3.unitZ), Vector3.unitX)
+    assertEquals(Vector3.unitX.cross(Vector3.unitZ), -Vector3.unitY)
+  }
+
   def to2dp(d: Double): Double =
     Math.round(d * 100).toDouble / 100