[vtkusers] ELLIPSE

Patric.Weis at mycrona.de Patric.Weis at mycrona.de
Wed Sep 13 03:54:33 EDT 2000

Hi Antonella,

you can use vtkQuadrics to evaluate and render an ellipsoid. The equation
of an ellipsoid is

     (x/a)^2 + (y/b)^2 +  (z/c)^2 = 1

so you only have to set the first 3 coefficents of the quadric equation.

An excellent side for further information can be found at

Here's a tcl snippet which may help:

# Quadric definition
  vtkQuadric ellipse
    ellipse SetCoefficients 0.5 0.5 1 0 0 0 0 0 0 0

  vtkSampleFunction sample
    sample SetSampleDimensions 30 30 30
    sample SetImplicitFunction ellipse

# Create the surface F(x,y,z) = constant
  vtkContourFilter contour
    contour SetInput [sample GetOutput]
    contour SetValue 0 0.5

  vtkPolyDataMapper contMapper
    contMapper SetInput [contour GetOutput]

  vtkActor contActor
    contActor SetMapper contMapper


Patric Weis

- - - Original Message - - -

   Anybody could you tell me if there is a class that computes the implicit
   function and function gradient for an ellipsoid as for sphere,cone etc?
   thanks in advance

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