Discussion Forum

I am using Comsol 3.5a and running a weak form system of PDEs on a roughly ellipsoid 3D geometry with the semi-major axis in the x-direction. (It looks like and represents an insect egg early in development.)

The typical experimental procedure for data collection involves positioning the egg on it side and measuring fluorescent surface intensity values at a series of x,y-coordinates along its semi-major axis.

I need to fit my model to data, so I need to extract concentration values from my model boundaries in a similar manner.

I can specify these x,y-coordinates, but I don't know the corresponding z-values (the geometry isn't perfectly elliptical). As a result, I can't simply plug everything into postinterp(fem, 'conc', [x y z]) and get my values.

Is there a way to interrogate the geometry to find "missing" boundary coordinate values? I.e., given (x,y) = (0.2,0.2), is there a way to return the corresponding z-values on all boundaries at that x,y-point.

I've looked at the geominfo() and postcoord() functions. While these have options to return points from the geometry (like vertices), they don't seem to handle simple geometric questions like mine. (Given x and y, what are corresponding boundary z-values?)

Has anyone found a way to do this? If possible, I'd like to avoid the hassle of defining x,y coordinates and finding nearest neighbors on the surface. These projected coordinates are messy and sometimes lead to NaNs from postinterp.

Thanks much!


Edit: I've also read through www.comsol.com/community/forums/general/thread/287/

It didn't address the question.