project mouse into view when clicking w/ mouse unlocked

Sources/Voxelotl/Math/VectorExtensions.swift

@@ -1,3 +1,23 @@
+import simd
+
+extension SIMD3 {
+  var xy: SIMD2<Scalar> {
+    get { .init(self.x, self.y) }
+    set {
+      self.x = newValue.x
+      self.y = newValue.y
+    }
+  }
+
+  var xz: SIMD2<Scalar> {
+    get { .init(self.x, self.z) }
+    set {
+      self.x = newValue.x
+      self.z = newValue.y
+    }
+  }
+}
+
 extension SIMD3 where Scalar: FloatingPoint {
   @inline(__always) static var X: Self      { Self(1, 0, 0) }
   @inline(__always) static var Y: Self      { Self(0, 1, 0) }
@@ -10,3 +30,42 @@ extension SIMD3 where Scalar: FloatingPoint {
   @inline(__always) static var forward: Self { -Z }
   @inline(__always) static var back: Self    {  Z }
 }
+
+extension SIMD3 where Scalar == Float {
+  static func * (q: simd_quatf, v: Self) -> Self {
+#if true
+    let q = simd_inverse(q)
+#else
+    let q = simd_quatf(real: q.real, imag: -q.imag)
+#endif
+
+#if true
+    var out = q.imag * 2 * simd_dot(q.imag, v)
+    out += v * (q.real * q.real - simd_dot(q.imag, q.imag))
+    return out + simd_cross(q.imag, v) * 2 * q.real
+#else
+    let uv = simd_cross(q.imag, v)
+    let uuv = simd_cross(q.imag, uv)
+    return v + ((uv * q.real) + uuv) * 2
+#endif
+  }
+}
+
+extension SIMD4 {
+  var xy: SIMD2<Scalar> {
+    get { .init(self.x, self.y) }
+    set {
+      self.x = newValue.x
+      self.y = newValue.y
+    }
+  }
+
+  var xyz: SIMD3<Scalar> {
+    get { .init(self.x, self.y, self.z) }
+    set {
+      self.x = newValue.x
+      self.y = newValue.y
+      self.z = newValue.z
+    }
+  }
+}