organise maths helpers

Sources/Voxelotl/Math/AABB.swift

@@ -0,0 +1,58 @@
+import simd
+
+struct AABB {
+  private var _bounds: simd_float2x3
+
+  var lower: SIMD3<Float> {
+    get { _bounds[0] }
+    set(row) { self._bounds[0] = row }
+  }
+  var upper: SIMD3<Float> {
+    get { _bounds[1] }
+    set(row) { self._bounds[1] = row }
+  }
+  var center: SIMD3<Float> {
+    get { (self._bounds[0] + self._bounds[1]) / 2 }
+  }
+  var size: SIMD3<Float> {
+    get { self._bounds[1] - self._bounds[0] }
+  }
+
+  var left: Float   { self._bounds[0].x }
+  var bottom: Float { self._bounds[0].y }
+  var far: Float    { self._bounds[0].z }
+  var right: Float  { self._bounds[1].x }
+  var top: Float    { self._bounds[1].y }
+  var near: Float   { self._bounds[1].z }
+
+  private init(bounds: simd_float2x3) {
+    self._bounds = bounds
+  }
+
+  init(from: SIMD3<Float>, to: SIMD3<Float>) {
+    self.init(bounds: .init(from, to))
+  }
+
+  static func fromUnitCube(position: SIMD3<Float> = .zero, scale: SIMD3<Float> = .one) -> Self {
+    self.init(
+      from: position - scale,
+      to:   position + scale)
+  }
+
+  func touching(_ other: Self) -> Bool{
+    let distLower = other._bounds[0] - self._bounds[1]  // x: left, y: bottom, z: far
+    let distUpper = self._bounds[0] - other._bounds[1]  // x: right, y: top, z: near
+
+    if distLower.x > 0 || distUpper.x > 0 { return false }
+    if distLower.y > 0 || distUpper.y > 0 { return false }
+    if distLower.z > 0 || distUpper.z > 0 { return false }
+
+    return true
+  }
+}
+
+extension AABB {
+  static func + (lhs: Self, rhs: SIMD3<Float>) -> Self {
+    .init(bounds: lhs._bounds + .init(rhs, rhs))
+  }
+}