[vtkusers] How to generate a surface normal glyph for a triangle cell

[Elvis Dowson]

Hi,
         The solution to this problem is to use the Tcl eval command,  
as follows

	eval arrowGlyphPoints InsertNextPoint [planeSource GetNormal]

This will expand the pointer to the normal co-ordinates, to a list, so  
that InsertNextPoint will get the x, y and z coordinate inputs.

Other alternative solutions to this problem can be found here: Nabble  
- VTK - Users - simple question about Tcl and VTK

Ok, so I got that fixed, but now I have a problem that I cannot  
explain. The output of the program is still wrong. The surface normal  
vector should be pointing perpendicular to the plane surface


How can I fix this? The arrow should be pointing upwards, from the  
plane surface.

Note that at some point, I decided to simplify the problem using a  
plane surface, try to solve the display of the surface normal first,  
before progressing on to display the surface normal glyph for a  
triangle cell.


Best regards,

Elvis Dowson

On Oct 8, 2008, at 11:02 AM, Elvis Dowson wrote:

> Hi,
>         I'm just trying to breakdown the problem. I'm just stuck at  
> one point below. Could someone help?
>
> arrowGlyphPoints InsertNextPoint [planeSource GetNormal]
>
> I have a plane source and I want to pass the plane normal to an  
> arrow glyph. I'm using vtkPoints to represent the location of the  
> arrow glyph. I can't seem to get the correct data type to be passed  
> from vtkPlanceSource::GetNormal() to vtkPoints::InsertNextPoint() in  
> TCL. I get the error message, Object named: arrowGlyphPoints, could  
> not find requested method: InsertNextPoint
> or the method was called with incorrect arguments.
>
> How can I fix the call to the above method in TCL?
>
> Here are the method declarations.
>
> vtkPoints::InsertPoints(const double x[3])
>
> virtual double* vtkPlaneSource::GetNormal()
> virtual void vtkPlaneSource::GetNormal(double data[3])
>
> Question: How can I pass data[3] or double * returned by  
> vtkPlaneSource::GetNormal() into vtkPoints::InsertNextPoint() ?
>
> Best regards,
>
> Elvis Dowson
>
>
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