VARKON Version 1.15 1997-10-16
A CUB_SUR is either defined by interpolation or by approximation.
Lets begin with a look at interpolation...
sur_splarr(id,method,nu,nv,p,tu,tv,twist);
Suppose we have a nu=10 by nv=20 rectangular grid of positions. In that
case p is a two-dimensional array of positions declared as follows...
VECTOR p(10,20);
Optional arrays declared the same way with tangents in the U-direction
(tu) and V-direction (tv) can be supplied as well as twist vectors (tw).
Any tangents not supplied will be splined using the Variable Stiffness
Spline algorithm and twist vectors will be calculated using the named method.
sur_splarr can also be used to interpolate data created in other
systems. Using MBS it is easy to open a file and copy data to internal
variables before calling sur_splarr.
Approximation is done using....
sur_approx(id,other_surface,"CUB_SUR",method,tol_1,tol_2);
The quality of the approximation is controlled by method and 2 optional
tolerance values. One method is to use a fix number of evenly distributed
patches. Another method is to let the system adjust the number of patches
so that a maximum value of positional error or error in normal direction
is not exceeded.
MBS can also be used to export a CUB_SUR. Patch coefficients are
available through a get routine and any geometric data is easy to retrieve
using on, norm or eval.
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