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<p class=MsoNormal><font size=3 color=blue face="Times New Roman"><span
style='font-size:12.0pt;color:blue'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>hi, thanks for the replies.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>i need to clarify one thing straight. the coloring i
am trying is not restricted to three orthogonal dimension as ugur assumed. for
each tensor, i need a set of colors calculated for each theta and phi direction
(in the spherical coordinates.) assuming a thetaResolution of 20 and
phiresolution of 20, color scalar array will be 400 scalars. i tried to explain
how i get the colors in the first message. basically a colour is calculated
from the surface normal and vector at that location (the vector is calculated
from the tensor by a scalar product of the tensor and the surface normal) (see
my first message below.) although the visualization idea is complicated, i know
that vtk script should not necessarily be as complex.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>a visualization task with vtk follows <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>source > filters> mapper > actor
>rendering<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>i understand i need to scale and aling a
vtkTensorGlyph using my tensor. then i need to create a vtkDoubleArray with 400
components using the same tensor and vtkTensorGlpyh surface normals. what
is not clear to me is: how to calculate the color array and store them in a
vtkDoubleArray from the tensor and surface normals. i suppose i need to
getSurfaceNormals and multiply them component by component with my tensor to
obtain another set of vectors. and with this new set i need to do scalar
multiplication with the surface normals to get the scalar color array.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span lang=EN-US style='font-size:12.0pt'>once i have a
scalar array i assign them to the vtkTensorGlyph, as luca wrote, with </span>vtkPolyData::GetPointData::SetScalars(array).<o:p></o:p></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>i am familiar with vtk theoretically and used it for straightforward tasks.
i will appreciate any help regarding how to practically create the color array.
btw i’m using java to write the scripts.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>cheers,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'>mecit yaman<o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><st1:PlaceType w:st="on"><font size=3
face="Times New Roman"><span lang=EN-US style='font-size:12.0pt'>university</span></font></st1:PlaceType><span
lang=EN-US> of <st1:PlaceName w:st="on">cape town</st1:PlaceName></span></st1:place><span
lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal><font size=3 color=blue face="Times New Roman"><span
style='font-size:12.0pt;color:blue'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=blue face="Times New Roman"><span
style='font-size:12.0pt;color:blue'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span lang=EN-US style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
Luca Pallozzi Lavorante [mailto:<st1:PersonName w:st="on">lplavorante@gmail.com</st1:PersonName>]
<br>
<b><span style='font-weight:bold'>Sent:</span></b> 25 July 2006 01:55 PM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">yaman@myhorizon.org</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [vtkusers] colour
mapping stress ellipsoids</span></font><span lang=EN-US><o:p></o:p></span></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Yaman, I do agree with
Ugur.<br>
I have used the vtkTensorGlyph class in order to get strain ellipsoids. I also
have tried to color the deformed object and, as far as I know, the only way is
to associate scalar values to the object´s points through the vtkFloatArray or
vtkDoubleArray. Once you created the array, the association is made via a call
like vtkPolyData::GetPointData::SetScalars(array).<br>
I hope this helps<br>
<br>
Luca<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal><span class=gmailquote><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>On 7/24/06, <b><span style='font-weight:bold'>Ugur
BOZKAYA</span></b> <<a href="mailto:u.bozkaya@fmcon.com">u.bozkaya@fmcon.com</a>>
wrote:</span></font></span><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Selam Mecit,<br>
<br>
As far as I know, there is no class for this purpose in VTK currently.<br>
vtkTensorGlyph and vtkGlyph3D can be used for typical tensor<br>
visualization. But the tensors are shown only in one color(RGB is also <br>
possible I guess, but it will not solve your problem). If you are<br>
familiar enough with VTK, you can change these classes for your purpose.<br>
Those glyph shapes such as ellipsoids (deformed spheres) are already<br>
defined as vtkPolyData, so you can use other shapes.<br>
<br>
I assume you are planning to use 3 orthogonal directions for coloring.<br>
You only need a vtkDataArray (e.g. vtkDoubleArray) with 3 components. So<br>
for each tensor location you will have 3 values. <br>
<br>
I guess it will be easier to write your own class which looks simpler.<br>
You will have your output as vtkPolyData, which is actually composed of<br>
your tensors. May be you can have a function which calculates a<br>
tensorshape(multicolored vtkPolyData) for a given location then you can<br>
add the output of this function to your volume output for each location.<br>
<br>
Good Luck,<br>
Ugur<br>
<br>
Mecit Yaman wrote:<br>
> hi,<br>
><br>
> i am trying to visualize second order tensors using stress ellipsoids with
a<br>
> different color mapping. the usual colouring is to map a scalar value,
e.g.<br>
> components, effective stress, trace or other scalars on the surface. i
want <br>
> to do a colouring where each point/polygon on the ellipsoid will be
coloured<br>
> differently. the color scheme is defined as follows:<br>
><br>
> the color along direction n(i) of the ellipsoid is obtained from the angle
<br>
> between the n(i), direction vector, and the stress vector along n(i). (the<br>
> stress vector along a direction can be obtained by multiplying the stress<br>
> tensor, T(ij) with the direction vector, n(i)). Thus: <br>
><br>
> T(ij) tensor<br>
> n(i) direction vector<br>
><br>
> stress vector(i) = T(ij) . n(i)<br>
><br>
> angle between stress vector and direction vector<br>
><br>
> cos(angle) = stress vector (i) . n(i) / ( |stress vector(i)| | n(i)|) <br>
><br>
> how does one colour map these angles, which are different for every<br>
> direction on an ellipsoid? do I need to change stress ellipsoid into a<br>
> polygonal data type? how do I calculate and store the angles in VTK? <br>
><br>
> i am able to render the icons in Mathematica, and will be happy to share<br>
> information with anyone interested.<br>
><br>
> thanks,<br>
><br>
> M Yaman<br>
> <st1:place w:st="on"><st1:PlaceType w:st="on">University</st1:PlaceType>
of <st1:PlaceName w:st="on">Cape Town</st1:PlaceName></st1:place><br>
> <br>
><br>
><br>
> _______________________________________________<br>
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><br>
<br>
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