Usage

A vtkPerspectiveTransform can be used to describe the full
range of homogeneous transformations. It was designed in
particular to describe a camera-view of a scene.
The order in which you set up the display coordinates (via
AdjustZBuffer() and AdjustViewport()), the projection (via
Perspective(), Frustum(), or Ortho()) and the camera view
(via SetupCamera()) are important. If the transform is in
PreMultiply mode, which is the default, set the Viewport and
ZBuffer first, then the projection, and finally the camera
view. Once the view is set up, the Translate and Rotate
methods can be used to move the camera around in world
coordinates. If the Oblique() or Stereo() methods are used,
they should be called just before SetupCamera().
In PostMultiply mode, you must perform all transformations
in the opposite order. This is necessary, for example, if
you already have a perspective transformation set up but
must adjust the viewport. Another example is if you have a
view transformation, and wish to perform translations and
rotations in the camera's coordinate system rather than in
world coordinates.
The SetInput and Concatenate methods can be used to create a
transformation pipeline with vtkPerspectiveTransform. See
vtkTransform for more information on the transformation
pipeline.
To create an instance of class vtkPerspectiveTransform,
simply invoke its constructor as follows

    obj = vtkPerspectiveTransform



 Methods

The class vtkPerspectiveTransform has several methods that
can be used. They are listed below. Note that the
documentation is translated automatically from the VTK
sources, and may not be completely intelligible. When in
doubt, consult the VTK website. In the methods listed below,
obj is an instance of the vtkPerspectiveTransform class.

* string = obj.GetClassName ()
* int = obj.IsA (string name)
* vtkPerspectiveTransform = obj.NewInstance ()
* vtkPerspectiveTransform = obj.SafeDownCast (vtkObject o)
* obj.Identity () - Set this transformation to the identity
  transformation. If the transform has an Input, then the
  transformation will be reset so that it is the same as the
  Input.
* obj.Inverse () - Invert the transformation. This will also
  set a flag so that the transformation will use the inverse
  of its Input, if an Input has been set.
* obj.AdjustViewport (double oldXMin, double oldXMax, double
  oldYMin, double oldYMax, double newXMin, double newXMax,
  double newYMin, double newYMax) - Perform an adjustment to
  the viewport coordinates. By default Ortho, Frustum, and
  Perspective provide a window of ([-1,+1],[-1,+1]). In
  PreMultiply mode, you call this method before calling
  Ortho, Frustum, or Perspective. In PostMultiply mode you
  can call it after. Note that if you must apply both
  AdjustZBuffer and AdjustViewport, it makes no difference
  which order you apply them in.
* obj.AdjustZBuffer (double oldNearZ, double oldFarZ, double
  newNearZ, double newFarZ) - Perform an adjustment to the
  Z-Buffer range that the near and far clipping planes map
  to. By default Ortho, Frustum, and Perspective map the
  near clipping plane to -1 and the far clipping plane to
  +1. In PreMultiply mode, you call this method before
  calling Ortho, Frustum, or Perspective. In PostMultiply
  mode you can call it after.
* obj.Ortho (double xmin, double xmax, double ymin, double
  ymax, double znear, double zfar) - Create an orthogonal
  projection matrix and concatenate it by the current
  transformation. The matrix maps [xmin,xmax], [ymin,ymax],
  [-znear,-zfar] to [-1,+1], [-1,+1], [+1,-1].
* obj.Frustum (double xmin, double xmax, double ymin, double
  ymax, double znear, double zfar) - Create an perspective
  projection matrix and concatenate it by the current
  transformation. The matrix maps a frustum with a back
  plane at -zfar and a front plane at -znear with extent
  [xmin,xmax],[ymin,ymax] to [-1,+1], [-1,+1], [+1,-1].
* obj.Perspective (double angle, double aspect, double
  znear, double zfar) - Create a perspective projection
  matrix by specifying the view angle (this angle is in the
  y direction), the aspect ratio, and the near and far
  clipping range. The projection matrix is concatenated with
  the current transformation. This method works via Frustum.
* obj.Shear (double dxdz, double dydz, double zplane) -
  Create a shear transformation about a plane at distance z
  from the camera. The values dxdz (i.e. dx/dz) and dydz
  specify the amount of shear in the x and y directions. The
  'zplane' specifies the distance from the camera to the
  plane at which the shear causes zero displacement.
  Generally you want this plane to be the focal plane. This
  transformation can be used in combination with Ortho to
  create an oblique projection. It can also be used in
  combination with Perspective to provide correct stereo
  views when the eye is at arbitrary but known positions
  relative to the center of a flat viewing screen.
* obj.Stereo (double angle, double focaldistance) - Create a
  stereo shear matrix and concatenate it with the current
  transformation. This can be applied in conjunction with
  either a perspective transformation (via Frustum or
  Projection) or an orthographic projection. You must
  specify the distance from the camera plane to the focal
  plane, and the angle between the distance vector and the
  eye. The angle should be negative for the left eye, and
  positive for the right. This method works via Oblique.
* obj.SetupCamera (double position[3], double focalpoint[3],
  double viewup[3]) - Set a view transformation matrix for
  the camera (this matrix does not contain any perspective)
  and concatenate it with the current transformation.
* obj.SetupCamera (double p0, double p1, double p2, double
  fp0, double fp1, double fp2, double vup0, double vup1,
  double vup2)
* obj.Translate (double x, double y, double z) - Create a
  translation matrix and concatenate it with the current
  transformation according to PreMultiply or PostMultiply
  semantics.
* obj.Translate (double x[3]) - Create a translation matrix
  and concatenate it with the current transformation
  according to PreMultiply or PostMultiply semantics.
* obj.Translate (float x[3]) - Create a translation matrix
  and concatenate it with the current transformation
  according to PreMultiply or PostMultiply semantics.
* obj.RotateWXYZ (double angle, double x, double y, double
  z) - Create a rotation matrix and concatenate it with the
  current transformation according to PreMultiply or
  PostMultiply semantics. The angle is in degrees, and
  (x,y,z) specifies the axis that the rotation will be
  performed around.
* obj.RotateWXYZ (double angle, double axis[3]) - Create a
  rotation matrix and concatenate it with the current
  transformation according to PreMultiply or PostMultiply
  semantics. The angle is in degrees, and (x,y,z) specifies
  the axis that the rotation will be performed around.
* obj.RotateWXYZ (double angle, float axis[3]) - Create a
  rotation matrix and concatenate it with the current
  transformation according to PreMultiply or PostMultiply
  semantics. The angle is in degrees, and (x,y,z) specifies
  the axis that the rotation will be performed around.
* obj.RotateX (double angle) - Create a rotation matrix
  about the X, Y, or Z axis and concatenate it with the
  current transformation according to PreMultiply or
  PostMultiply semantics. The angle is expressed in degrees.
* obj.RotateY (double angle) - Create a rotation matrix
  about the X, Y, or Z axis and concatenate it with the
  current transformation according to PreMultiply or
  PostMultiply semantics. The angle is expressed in degrees.
* obj.RotateZ (double angle) - Create a rotation matrix
  about the X, Y, or Z axis and concatenate it with the
  current transformation according to PreMultiply or
  PostMultiply semantics. The angle is expressed in degrees.
* obj.Scale (double x, double y, double z) - Create a scale
  matrix (i.e. set the diagonal elements to x, y, z) and
  concatenate it with the current transformation according
  to PreMultiply or PostMultiply semantics.
* obj.Scale (double s[3]) - Create a scale matrix (i.e. set
  the diagonal elements to x, y, z) and concatenate it with
  the current transformation according to PreMultiply or
  PostMultiply semantics.
* obj.Scale (float s[3]) - Create a scale matrix (i.e. set
  the diagonal elements to x, y, z) and concatenate it with
  the current transformation according to PreMultiply or
  PostMultiply semantics.
* obj.SetMatrix (vtkMatrix4x4 matrix) - Set the current
  matrix directly. This actually calls Identity(), followed
  by Concatenate(matrix).
* obj.SetMatrix (double elements[16]) - Set the current
  matrix directly. This actually calls Identity(), followed
  by Concatenate(matrix).
* obj.Concatenate (vtkMatrix4x4 matrix) - Concatenates the
  matrix with the current transformation according to
  PreMultiply or PostMultiply semantics.
* obj.Concatenate (double elements[16]) - Concatenates the
  matrix with the current transformation according to
  PreMultiply or PostMultiply semantics.
* obj.Concatenate (vtkHomogeneousTransform transform) -
  Concatenate the specified transform with the current
  transformation according to PreMultiply or PostMultiply
  semantics. The concatenation is pipelined, meaning that if
  any of the transformations are changed, even after
  Concatenate() is called, those changes will be reflected
  when you call TransformPoint().
* obj.PreMultiply () - Sets the internal state of the
  transform to PreMultiply. All subsequent operations will
  occur before those already represented in the current
  transformation. In homogeneous matrix notation, M = M*A
  where M is the current transformation matrix and A is the
  applied matrix. The default is PreMultiply.
* obj.PostMultiply () - Sets the internal state of the
  transform to PostMultiply. All subsequent operations will
  occur after those already represented in the current
  transformation. In homogeneous matrix notation, M = A*M
  where M is the current transformation matrix and A is the
  applied matrix. The default is PreMultiply.
* int = obj.GetNumberOfConcatenatedTransforms () - Get the
  total number of transformations that are linked into this
  one via Concatenate() operations or via SetInput().
* vtkHomogeneousTransform = obj.GetConcatenatedTransform
  (int i) - Set the input for this transformation. This will
  be used as the base transformation if it is set. This
  method allows you to build a transform pipeline: if the
  input is modified, then this transformation will
  automatically update accordingly. Note that the
  InverseFlag, controlled via Inverse(), determines whether
  this transformation will use the Input or the inverse of
  the Input.
* obj.SetInput (vtkHomogeneousTransform input) - Set the
  input for this transformation. This will be used as the
  base transformation if it is set. This method allows you
  to build a transform pipeline: if the input is modified,
  then this transformation will automatically update
  accordingly. Note that the InverseFlag, controlled via
  Inverse(), determines whether this transformation will use
  the Input or the inverse of the Input.
* vtkHomogeneousTransform = obj.GetInput () - Set the input
  for this transformation. This will be used as the base
  transformation if it is set. This method allows you to
  build a transform pipeline: if the input is modified, then
  this transformation will automatically update accordingly.
  Note that the InverseFlag, controlled via Inverse(),
  determines whether this transformation will use the Input
  or the inverse of the Input.
* int = obj.GetInverseFlag () - Get the inverse flag of the
  transformation. This controls whether it is the Input or
  the inverse of the Input that is used as the base
  transformation. The InverseFlag is flipped every time
  Inverse() is called. The InverseFlag is off when a
  transform is first created.
* obj.Push () - Pushes the current transformation onto the
  transformation stack.
* obj.Pop () - Deletes the transformation on the top of the
  stack and sets the top to the next transformation on the
  stack.
* vtkAbstractTransform = obj.MakeTransform () - Make a new
  transform of the same type – you are responsible for
  deleting the transform when you are done with it.
* int = obj.CircuitCheck (vtkAbstractTransform transform) -
  Check for self-reference. Will return true if
  concatenating with the specified transform, setting it to
  be our inverse, or setting it to be our input will create
  a circular reference. CircuitCheck is automatically called
  by SetInput(), SetInverse(), and Concatenate(vtkXTransform
  *). Avoid using this function, it is experimental.
* long = obj.GetMTime () - Override GetMTime to account for
  input and concatenation.


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