Function PyUtilComputeNormalFromlPoints

Code/Source/PythonAPI/PyUtils.cxx:608–644

-------------------------------- PyUtilComputeNormalFromlPoints -------------------------------- Compute a normal from a list of points.

// Compute a normal from a list of points. 
//
std::array<double,3>
PyUtilComputeNormalFromlPoints(const std::vector<std::array<double,3>>& points)
{
  std::array<double,3> normal;

  if (points.size() < 3) {
      throw std::runtime_error("[PyUtilComputeNormalFromlPoints] The number of points is < 3.");
  }

  int numPoints = points.size();
  double nx = 0.0, ny = 0.0, nz = 0.0, mag;
  int j;

  for (int i = 0; i < numPoints; i++) {
      if (i == (numPoints - 1)) {
          j = 0;
      } else {
          j = i + 1;
      }

      nx += points[j][2]*points[i][1] - points[j][1]*points[i][2];
      ny += points[j][0]*points[i][2] - points[j][2]*points[i][0];
      nz += points[j][1]*points[i][0] - points[j][0]*points[i][1];
  }

  mag = sqrt(nx*nx + ny*ny + nz*nz);

  if (mag == 0.0) {
      throw std::runtime_error("[PyUtilComputeNormalFromlPoints] Points produced a magnitude zero normal.");
  }

  normal[0] = nx / mag;
  normal[1] = ny / mag;
  normal[2] = nz / mag;

  return normal;
}

//------------------------
// PyUtilSetupApiFunction