#ifndef IGL_UNPROJECT_ON_PLANE_H
#define IGL_UNPROJECT_ON_PLANE_H

#include <Eigen/Core>

namespace igl
{
  // Given a screen space point (u,v) and the current projection matrix (e.g.
  // gl_proj * gl_modelview) and viewport, _unproject_ the point into the scene
  // so that it lies on given plane.
  //
  // Inputs:
  //   UV  2-long uv-coordinates of screen space point
  //   M  4 by 4 projection matrix
  //   VP  4-long viewport: (corner_u, corner_v, width, height)
  //   P  4-long plane equation coefficients: P*(X 1) = 0
  // Outputs:
  //   Z  3-long world coordinate
  template <
    typename DerivedUV,
    typename DerivedM,
    typename DerivedVP,
    typename DerivedP,
    typename DerivedZ>
  void unproject_on_plane(
    const Eigen::MatrixBase<DerivedUV> & UV,
    const Eigen::MatrixBase<DerivedM> & M,
    const Eigen::MatrixBase<DerivedVP> & VP,
    const Eigen::MatrixBase<DerivedP> & P,
    Eigen::PlainObjectBase<DerivedZ> & Z);
}

#ifndef IGL_STATIC_LIBRARY
#  include "unproject_on_plane.cpp"
#endif

#endif