<div dir="ltr"><div><div><div><div>Hi Ralf,<br><br></div>The shape of the FOD is easy to interpret: you basically start with a (unit) sphere, and then scale its radius along each orientation by the FOD amplitude for that orientation. It's basically the 3D version of polar coordinates ( <a href="http://en.wikipedia.org/wiki/Polar_coordinate_system">http://en.wikipedia.org/wiki/Polar_coordinate_system</a> ), but used to represent a 2D spherical function in a 3D space.<br>
</div>The RGB values for the colors are simply derived from a normalized vector that points along each direction. The colors are nothing more than a visual aid though; they help you navigate a field of FODs much easier.<br>
<br></div>The caption in figure 7 refers you to the webversion, because the printed version probably did not feature colors at the time. The word "interpretation" there, only means that whatever is written in the caption about colors, can only really be visually appreciated in the (colored) digital version. The normal PDF at Elsevier basically is that web version. :-)<br>
<br></div>Hope this clarifies some things!<br><br>Cheers,<br>Thijs<br><div><br></div></div><div class="gmail_extra"><br clear="all"><div><div dir="ltr"><span style="color:rgb(68,68,68)"><b><font size="4">Thijs Dhollander</font><br>
<font><a href="mailto:thijs.dhollander@gmail.com" target="_blank">thijs.dhollander@gmail.com</a><br>Tel. +32 475 36 44 27</font></b><br><font size="1">Medical Image Computing (MIC), ESAT-PSI, Department of Electrical Engineering, KU Leuven</font></span></div>
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<br><br><div class="gmail_quote">On Mon, Apr 28, 2014 at 3:46 PM, Luetzkendorf, Ralf <span dir="ltr"><<a href="mailto:Ralf.Luetzkendorf@med.ovgu.de" target="_blank">Ralf.Luetzkendorf@med.ovgu.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hello MRTrix Community,<br>
<br>
I have a question about the color and shape of the FODs / ODFs<br>
I read through the papers and I have to be absolutely sure how to interpret them.<br>
<br>
At first in the Paper "Direct estimation of the fiber orientation density function from diffusion-weighted MRI data using spherical deconvolution, 2004" Figure 7 referred you to a web version for color interpretation. Is there still a Web Version? I only found the normal PDF at Elsevier.<br>
<br>
Do these drop-shaped geometrical bodies, that face each other have exactly the same color? And its only a rendering problem, that they very often don't have it in figures, like in Figure 7 of the 2004 Article?<br>
<br>
Is there a description how to interpret the shape of the ODF /FOD. Something like a first and still established paper about it?<br>
<br>
Thanks for the help,<br>
<br>
Ralf<br>
<br>
<br>
<br>
<br>
<br>
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