Add doc.

include/igl/predicates/predicates.cpp

@@ -1,3 +1,10 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2019 Qingnan Zhou <qnzhou@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/.
 #include <igl/predicates/predicates.h>
 #include <predicates.h>
 

include/igl/predicates/predicates.h

@@ -1,3 +1,10 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2019 Qingnan Zhou <qnzhou@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/.
 #pragma once
 #ifndef IGL_PREDICATES_PREDICATES_H
 #define IGL_PREDICATES_PREDICATES_H
@@ -13,12 +20,30 @@ namespace igl {
       COLLINEAR=0, COPLANAR=0, COCIRCULAR=0, COSPHERICAL=0, DEGENERATE=0
     };
 
+    // Compute the orientation of the triangle formed by pa, pb, pc.
+    //
+    // Input:
+    //   pa, pb, pc  2D points.
+    //
+    // Output:
+    //   Return POSITIVE if pa, pb, pc is counterclockwise oriented.
+    //          NEGATIVE if they are clockwise oriented.
+    //          COLLINEAR if they are collinear.
     template<typename Vector2D>
     IGL_INLINE Orientation orient2d(
         const Eigen::MatrixBase<Vector2D>& pa,
         const Eigen::MatrixBase<Vector2D>& pb,
         const Eigen::MatrixBase<Vector2D>& pc);
 
+    // Compute the orientation of the tetrahedron formed by pa, pb, pc, pd.
+    //
+    // Input:
+    //   pa, pb, pc, pd  3D points.
+    //
+    // Output:
+    //   Return POSITIVE if pd is "below" the oriented plane formed by pa, pb and pc.
+    //          NEGATIVE if pd is "above" the plane.
+    //          COPLANAR if pd is on the plane.
     template<typename Vector3D>
     IGL_INLINE Orientation orient3d(
         const Eigen::MatrixBase<Vector3D>& pa,
@@ -26,6 +51,16 @@ namespace igl {
         const Eigen::MatrixBase<Vector3D>& pc,
         const Eigen::MatrixBase<Vector3D>& pd);
 
+    // Decide whether a point is inside/outside/on a circle.
+    //
+    // Input:
+    //   pa, pb, pc  2D points that defines an oriented circle.
+    //   pd          2D query point.
+    //
+    // Output:
+    //   Return INSIDE if pd is inside of the circle defined by pa, pb and pc.
+    //          OUSIDE if pd is outside of the circle.
+    //          COCIRCULAR pd is exactly on the circle.
     template<typename Vector2D>
     IGL_INLINE Orientation incircle(
         const Eigen::MatrixBase<Vector2D>& pa,
@@ -33,6 +68,16 @@ namespace igl {
         const Eigen::MatrixBase<Vector2D>& pc,
         const Eigen::MatrixBase<Vector2D>& pd);
 
+    // Decide whether a point is inside/outside/on a sphere.
+    //
+    // Input:
+    //   pa, pb, pc, pd  3D points that defines an oriented sphere.
+    //   pe              3D query point.
+    //
+    // Output:
+    //   Return INSIDE if pe is inside of the sphere defined by pa, pb, pc and pd.
+    //          OUSIDE if pe is outside of the sphere.
+    //          COSPHERICAL pd is exactly on the sphere.
     template<typename Vector3D>
     IGL_INLINE Orientation insphere(
         const Eigen::MatrixBase<Vector3D>& pa,