<div dir="ltr"><div><div><div>Hi Jian Cheng,<br><br></div>Many thanks for your feedback. I will follow your suggestion for point #1. For point #2, would you have a rule of thumb to estimate the quality of the scheme? Once one has the (min, max, mean, std) statistics, how to assess the scheme quality? For example what would you say of the quality of the 60-shell, 90-shell and 60x90 scheme I provided and why would you reach your conclusion?<br><br></div>Best,<br><br></div>Michael<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, May 17, 2016 at 3:25 PM, Jian Cheng <span dir="ltr"><<a href="mailto:jian.cheng.1983@gmail.com" target="_blank">jian.cheng.1983@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Hi Michael, <br>
<br>
Thanks for your feedback. <br>
<br>
1) SamplingSchemeQSpaceIMOCEstimation implemented IMOC method
proposed in the paper <br>
<a href="https://hal.archives-ouvertes.fr/hal-01154774/file/sampling_MICCAI2015.pdf" target="_blank">https://hal.archives-ouvertes.fr/hal-01154774/file/sampling_MICCAI2015.pdf</a><br>
It is a greedy method which can provide an initialization for
optimization method (CNLO) to get a further improved scheme. <br>
I will release CNLO later when I have time. At this moment, you
can just use IMOC for your task. <br>
<br>
You cannot use tessellation order more than 7 directly for
SamplingSchemeQSpaceIMOCEstimation, because it uses the stored
gradient tables in ~/.dmritool/Data/Tessellation. You did not see
the warning message because you build the code with
VERBOSITY_LEVEL=0. I just modified the code and pushed it to
github so that you can see the warning message. <br>
If you want to try tessellation order more than 7, you can use: <br>
SphereTessellator --tessorder 8 --hemisphere grad_t8.txt<br>
SamplingSchemeQSpaceIMOCEstimation grad.txt --numberOfSamples
60,90 --fineOrientations grad_t8.txt<br>
In my laptop, it takes 18 seconds. <br>
Tessellation order of 7 is much faster, and practically enough for
your usage. <br>
<br>
2) For the shell with 60 samples, there is a minimal angle for
each sample. Then we have 60 minimal angles. <span style="font-family:monospace,monospace">OrientationStatistics
shows (min, max, mean, std)</span> for these 60 minimal angles,
also for shell with 90 samples and the combined shell with 150
samples. <br>
<br>
best,<br>
Jian Cheng<div><div class="h5"><br>
<br>
On 05/17/2016 01:24 PM, Michael Dayan wrote:<br>
</div></div></div>
<blockquote type="cite"><div><div class="h5">
<div dir="ltr">
<div>
<div>dmritool has been very useful to generate multi-shell
scheme but I would like to know more about the optimal
protocol to generate such shemes:<br>
<br>
</div>
1) Is SamplingSchemeQSpaceIMOCEstimation the most adequate
function for this purpose? What parameters to change to
improve the results? I tried to use higher "tesselate orders"
than 7 (e.g. 8, 11, ...) but kept getting a "Segmentation
fault (core dumped)" error.<br>
<br>
</div>
2) To assess the quality of the results how to interpret the
statistics of the generated scheme, in particular the minimum
and maximum angle values? Below is an example of statistics for
a 2-shell scheme with 60 and 90 directions in the first and
second shell.<br>
<br>
<span style="font-family:monospace,monospace"> OrientationStatistics
imoc_60x90_shell1.txt imoc_60x90_shell2.txt --combine<br>
file: imoc_60x90_shell1.txt<br>
size = 60<br>
60 unique samples, 0 antipodal samples, 0 repeated samples.<br>
minimal angle = 14.1538, radian=0.24703 (covering radius)<br>
maximal angle = 14.7301, radian=0.257089<br>
mean angle = 14.3346<br>
std angle = 0.144217<br>
upper bound (120 points) = 19.9391, radian=0.348003<br>
upper bound (60 points) = 28.2194, radian=0.492521<br>
electrostaticEnergy (order=2) = 3.05481<br>
electrostaticEnergy (order=1) = 1.98694<br>
<br>
file: imoc_60x90_shell2.txt<br>
size = 90<br>
90 unique samples, 0 antipodal samples, 0 repeated samples.<br>
minimal angle = 11.5536, radian=0.201648 (covering radius)<br>
maximal angle = 19.6656, radian=0.34323<br>
mean angle = 12.3677<br>
std angle = 1.45567<br>
upper bound (180 points) = 16.2761, radian=0.284071<br>
upper bound (90 points) = 23.0295, radian=0.401941<br>
electrostaticEnergy (order=2) = 2.8735<br>
electrostaticEnergy (order=1) = 1.92306<br>
<br>
Combine 2 orientations<br>
size = 150<br>
150 unique samples, 0 antipodal samples, 0 repeated samples.<br>
minimal angle = 8.95306, radian=0.15626 (covering radius)<br>
maximal angle = 14.4468, radian=0.252144<br>
mean angle = 10.2967<br>
std angle = 1.42696<br>
upper bound (300 points) = 12.6048, radian=0.219995<br>
upper bound (150 points) = 17.8313, radian=0.311216<br>
electrostaticEnergy (order=2) = 2.79829<br>
electrostaticEnergy (order=1) = 1.89174<br>
Spherical code cost function = 0.1903</span><br>
<br>
<br>
</div>
<br>
<fieldset></fieldset>
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