find the angle between the vectors connecting each point with (0,0,0).
compute the fraction of the circle that it represents, and multiply it by:
K * PI * D
where
D = diameter of ?h.sphere
K = sqrt(surface area of surface you are interested in)
---------------------------------------------------
sqrt(surface area of sphere)
cheers
Bruce
On
Tue, 25 Oct 2011, Steph Bickel wrote:
Hi Rudolph and Bruce,
thanks for your responses.
rudolph, your example works great. just 2 questions:
what dimension is the total path cost in the mris_pmake output?
is there a way to input a file with several vertex point pairs to compute
the distance between, or do I have to loop through the pairs I would like to
compute?
Bruce, thank you very much for your suggestion. it would be easier for me to
compute it this way and I would like to compare results with mris_pmake
results. I am currently looking for a way to compute the distance on the
sphere, if you have a suggestion how to do this it would be much
appreciated.
Thank you,
Stephan
On Tue, Oct 25, 2011 at 2:26 PM, Rudolph Pienaar
<rudo...@nmr.mgh.harvard.edu> wrote:
On 10/25/11 10:57 , Steph Bickel wrote:
Hi Rudolph,
thanks for your speedy response.
I want to get distance along vertices (the surface)
between two vertex
points.
OK -- 'mris_pmake' works for this. Say you have a subject called
'test' and you want to calculate the distance on the lh 'smoothwm'
from vertex 1000 to 20000:
mris_pmake --subject test --hemi lh --surface0 smoothwm --surface1
smoothwm --curv0 curv --curv1 curv --mpmProg pathFind --mpmOverlay
distance --mpmArgs startVertex:1000,endVertex:20000
The only important options are '--surface0 smoothwm --mpmProg pathFind
--mpmOverlab distance --mpmArgs startVertex:1000,endVertex:20000'
The other args, '--surface 1 smoothwm --curv0 curv --curv1 curv' are
not used for finding the path, but do nonetheless need to be filled
in. As I indicated, "mris_pmake" is more developer than user friendly.
So, the above will generate in your terminal:
Start->End vertices [ 1000->20000 ]
Total path cost [ 55.957047 ]
LabelWrite: saving to ./dijk.label
Where the "Total path cost" corresponds to the distance along the mesh
(using the "distance" overlay in the "pathFind" module between
vertices 1000 and 20000 means that the minimum cost in moving between
those locations is the minimum distance).
You can load the 'dijk.label' into Freeview to see the path itself.
If you want to use the 'inflated' surface instead, change the arg to
'--surface0':
mris_pmake --subject test --hemi lh --surface0 inflated --surface1
smoothwm --curv0 curv --curv1 curv --mpmProg pathFind --mpmOverlay
distance --mpmArgs startVertex:1000,endVertex:20000
which outputs:
Start->End vertices [ 1000->20000 ]
Total path cost [ 57.521545 ]
LabelWrite: saving to ./dijk.label
Oh, and I have a strong suspicion that you need to use the current
'dev' version of 'mris_pmake'. If you are using the 'stable' version
and it won't work, let me know and we can get the 'dev' version out to
you.
Best
-=R
--
Rudolph Pienaar, M.Eng, D.Eng / email: rudo...@nmr.mgh.harvard.edu
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging
149 (2301) 13th Street, Charlestown, MA 02129 USA
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