Method Shear

Common/Transforms/vtkPerspectiveTransform.cxx:362–381

------------------------------------------------------------------------------ The Shear method can be used after Perspective to create correct perspective views for use with head-tracked stereo on a flat, fixed (i.e. not head-mounted) viewing screen. You must measure the eye position relative to the center of the RenderWindow (or the center of the screen, if the window is full-screen). The foll

// tried any of this except for with pencil & paper.  Looks good on
// paper, though!
void vtkPerspectiveTransform::Shear(double dxdz, double dydz, double zplane)
{
  double matrix[4][4];
  vtkMatrix4x4::Identity(*matrix);

  // everything is negative because the position->focalpoint vector
  // is in the -z direction, hence z distances along that vector
  // are negative.

  // shear according to the eye position relative to the screen
  matrix[0][2] = -dxdz;
  matrix[1][2] = -dydz;

  // shift so that view rays converge in the focal plane
  matrix[0][3] = -zplane * dxdz;
  matrix[1][3] = -zplane * dydz;

  // concatenate with the current matrix
  this->Concatenate(*matrix);
}

//------------------------------------------------------------------------------
// For convenience -- this is sufficient for most people's stereo needs.