
 Usage

Detect the edges of the image renderered by its delegate.
Edge-detection uses a Sobel high-pass filter (3x3 kernel).
This pass expects an initialized depth buffer and color
buffer. Initialized buffers means they have been cleared
with farest z-value and background color/gradient/
transparent color. An opaque pass may have been performed
right after the initialization.
The delegate is used once.
Its delegate is usually set to a vtkCameraPass or to a post-
processing pass.
This pass requires a OpenGL context that supports texture
objects (TO), framebuffer objects (FBO) and GLSL. If not, it
will emit an error message and will render its delegate and
return.
.SECTION Implementation To compute the gradient magnitude,
the x and y components of the gradient (Gx and Gy) have to
be computed first. Each computation of Gx and Gy uses a
separable filter. The first pass takes the image from the
delegate as the single input texture. The first pass has two
outputs, one for the first part of Gx, Gx1, result of a
convolution with (-1 0 1), one for the first part of Gy,
Gy1, result of a convolution with (1 2 1). The second pass
has two inputs, Gx1 and Gy1. Kernel (1 2 1)^T is applied to
Gx1 and kernel (-1 0 1)^T is applied to Gx2. It gives the
values for Gx and Gy. Thoses values are then used to compute
the magnitude of the gradient which is stored in the render
target. The gradient computation happens per component
(R,G,B). A is arbitrarly set to 1 (full opacity).
To create an instance of class
vtkSobelGradientMagnitudePass, simply invoke its constructor
as follows

    obj = vtkSobelGradientMagnitudePass



 Methods

The class vtkSobelGradientMagnitudePass 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 vtkSobelGradientMagnitudePass
class.

* string = obj.GetClassName ()
* int = obj.IsA (string name)
* vtkSobelGradientMagnitudePass = obj.NewInstance ()
* vtkSobelGradientMagnitudePass = obj.SafeDownCast
  (vtkObject o)
* obj.ReleaseGraphicsResources (vtkWindow w) - Release
  graphics resources and ask components to release their own
  resources.


    Precondition:
        w_exists: w!=0



* FreeMat_Documentation
* Visualization_Toolkit_Rendering_Classes
* Generated on Thu Jul 25 2013 17:18:35 for FreeMat by
  doxygen_ 1.8.1.1

