[vtkusers] Displaying certain normal

[Naoko TAKAYA]

Dear VTK-users

I have a very simple question.

I want to display the normal at a certain point on the sphere.

I have a sphere with the center at (-12, -14, 14) and the 
radius = 8.0. 

I just want to display the normal of this sphere at a point (-12,-7, 10).

Thank you in advance ;-)

Naoko.T

The brief code is the following:
-----------------------------------------------------------
vtkSphereSource *vSphere = vtkSphereSource::New();
vSphere -> SetRadius(8.0);
vSphere -> SetCenter(-12, -14, 14);
vSphere -> SetPhiResolution(20);
vSphere -> SetThetaResolution(20);
vtkConeSource *vCone = vtkConeSource::New();
vCone -> SetResolution(6);
vCone -> SetHeight(8);
vCone -> SetRadius(2);
vtkGlyph3D *vGlyphPoints = vtkGlyph3D::New();
vGlyphPoints -> SetInput(???);
vGlyphPoints -> SetSource(???);
-----------------------------------------------------------

******************************************************

Naoko Takaya 
Computer Vision Laboratory
Department Computer Science
Faculty of Science and Engineering
Ritsumeikan University

e-mail: takaya at cv.cs.ritsumei.ac.jp

*******************************************************