[vtkusers] How to size glyphs with one scalar field, and colour with another?

[Craig N. Scott]

I had to do something similar myself recently, only with scalars and
vectors (not fields). I got little response from the mailing list, but I
eventually worked out a solution using vtkProgammableGlyphFilter. It
involves saving the scalar data array to be used for scaling, then
setting the scalar array for the reader to the one I wanted to color by.
What follows is a brief snippet of Tcl code. It should draw spheres with
radius corresponding to a scalar point data set called "radius" and
color the spheres  according to a different scalar point data set called
"colorValues". I haven't tested the code below (I've pulled it out from
pieces of some of my work), but it should do the trick.

PS: I don't claim that it is good Tcl coding style, nor particularly
efficient!
======================================

vtkUnstructuredGridReader  reader
reader SetFileName "something.vtk"

reader SetScalarsName "radius"
reader Update
  
set srcArray [[[reader GetOutput] GetPointData] GetArray "radius"] 

vtkDoubleArray radiusArray
radiusArray DeepCopy $srcArray
  
reader SetScalarsName "colorValues"

vtkSphereSource sphere

# procedure for generating glyphs
proc Glyph {} {
   set ptId [glypher GetPointId]
   set xyz  [glypher GetPoint]
   set x [lindex $xyz 0] 
   set y [lindex $xyz 1] 
   set z [lindex $xyz 2] 

   set radius [radiusArray GetTuple1 $ptId]
   
   eval sphere SetRadius $radius
   eval sphere SetCenter $xyz
}

vtkProgrammableGlyphFilter glypher
glypher SetInput [reader GetOutput]
glypher SetSource [sphere GetOutput]
glypher SetGlyphMethod {Glyph}

vtkDataSetMapper resultMapper
resultMapper SetInput [glypher GetOutput]

 :
 (set up an actor, renderer, etc. as per usual)
 :


On Tue, 2004-10-19 at 13:54, s comp wrote:
> Hi All,
>  
> How can I size glyphs with one scalar field and colour them with
> another?
>  
> Thanks,
>  
> Sonam

-- 
Dr Craig Scott, CSIRO (CMIS)
Melbourne, Australia

Computers are easy to reboot. Attitudes are much harder.