Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/libigl/igl/rotate_by_quat.h

@@ -0,0 +1,33 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
+// 
+// This Source Code Form is subject to the terms of the Mozilla Public License 
+// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
+// obtain one at http://mozilla.org/MPL/2.0/.
+#ifndef IGL_ROTATE_BY_QUAT_H
+#define IGL_ROTATE_BY_QUAT_H
+#include "igl_inline.h"
+
+namespace igl
+{
+  // Compute rotation of a given vector/point by a quaternion
+  // A Quaternion, q, is defined here as an arrays of four scalars (x,y,z,w),
+  // such that q = x*i + y*j + z*k + w
+  // Inputs:
+  //   v  input 3d point/vector
+  //   q  input quaternion
+  // Outputs:
+  //   out  result of rotation, allowed to be same as v
+  template <typename Q_type>
+  IGL_INLINE void rotate_by_quat(
+    const Q_type *v,
+    const Q_type *q, 
+    Q_type *out);
+};
+
+#ifndef IGL_STATIC_LIBRARY
+#  include "rotate_by_quat.cpp"
+#endif
+
+#endif