Having obtained data points of the surface you are trying to fit a mesh to (digitising), and creating an initial mesh (initial-mesh) that is to be deformed to fit these points, you now need to do the fitting.

Begin by typing `cm` at the prompt. All of the following commands
are in fit.com, which you can run from
the command prompt by typing `cm fit.com`.

Begin by reading in the array sizes we need, defining the coorindate system,
and then defining the initial mesh:

fem def para;r;fit fem def coord 3,1 fem def base;r;bicubic-sector fem def node;r;epi-init fem def elem;r;epi-initWe have now created the initial mesh. We can view it by typing the following at the

fem def win;c on yz # Define a window on the yz plane fem draw lineWe should now read in the data points for the mesh to be fitted to, and then calculate the Xi positions (The positions of the data in terms of local element space) of the data:

fem def data;r;epi fem def xi;c close

Having set up the initial mesh and data, we now have to create space
inside `cm` to store the fitted nodal and element parameters.
You can create this by:

fem def field;r;epi # To create a field to fit the nodal geometry fem def elem;r;epi field # To create a field to fit the elemental geometry

We can now define the fitting procedure and fit the data. Define the fitting procedure by:

fem def fit;r;epi geometryYou will notice in the .ipfit file there are parameters there for smoothing via Sobolev weights on the derivatives. These weights are used to remove excessive 'wrinkling' of the fitted surface to your data. The smaller these numbers are, the closer the fit 'hugs' the data and the more wrinkled it can become. A good range is between 10.0E-1 to 10.0E-6. These parameters are the main variables that you can control to ensure a good quality fit.

Now fit the data:

fem fit fem update node fit # Overwrites nodes with new, fitted ones.

You can check out your fitting by re-drawing the lines inside `cm`:

fem hide lines fem draw lines

Having fitted the data once, you should see output from the
`fem fit` command, giving you RMS error. If this is
more than what might be desired, you can run the fit again
on the new mesh to reduce the RMS error again. The amount that
this decreases by is limited, however, so there is no point
in doing it until your ears fall off. To repeat the process,
type the following:

fem def xi;c close # Redefine the Xi positions of the data points fem fit fem update node fit

There is a comfile that uses the files you have exported
to view the mesh in `cmgui`. This exists in
view.com. You can run it
by simply typing in:

cmgui viewAnd you should see an image like the following:

#Example 21e3

Name Modified Size

example_21e3.com 09-Feb-2001 14 epi/ 13-Apr-2007 - lv/ 13-Apr-2007 - rv/ 13-Apr-2007 -

Name Modified Size

examples_2_21_21e_21e3.tar.gz 14-Apr-2007 88k

Html last generated: Sun Mar 6 05:50:10 2016

Input last modified: Fri Apr 13 10:30:57 2007

CMISS Help / Examples / 2 / 21 / 21e / 21e3