I'll second what Derek said, but I'd also like to ask if you are doing
some kind of gradient recovery at the nodal points of a C^0 finite
element discretization? There was a discussion about this particular
topic a couple days ago...
On Thu, Dec 11, 2008 at 1:28 PM, Derek Gaston <friedmud@...> wrote:
> MeshFunction can do this for you. Just initialize it with your
> solution vector and then you can ask for the gradient at arbitrary
> physical points.
> Now... just FYI.... if you just want to search you can use a
> PointLocator class... which returns an Elem based on a physical point.
> On Dec 11, 2008, at 12:15 PM, bkraczek wrote:
>> I'm looking for a way to obtain the gradient of my 3d FE solution at a
>> specified point or points. I imagine this entails two parts, neither
>> which I know how to do:
>> 1. Figure out which element a point lies inside
>> 2. Determine the gradient of the basis functions inside that element.
>> For the first part, if there is a way to do this already in the
>> code, how
>> do you go about it? If there isn't a way to do this already in the
>> code, I
>> think I could generate a way to do this from the coordinates of the
>> How do I obtain these within a program?
>> For the second part, once I know which element the point lies inside
>> I need
>> to calculate the gradient at that point. I was trying to figure out
>> how to
>> do this based on how dphi is calculated, but I cannot find where
>> that is
>> actually done in the code. I can find its declaration in fe_base.h,
>> but not
>> where it is calculated.