Varkon Geometry Tutorial: Trimming of Surfaces 2006-04-17

Trimming of Surfaces

In most CAD systems a trimmed surface is defined with a base (un-trimmed) surface with a closed curve on the surface that defines the part of interest, i.e. the trimmed surface. For Solids are such bounded surfaces called Faces.
Varkon does not support trimmed surfaces (Faces). The necessary type of surface boundary curves (called UV-curves) are implemented, but not the functionality to automatically trim the curves that is outside the closed boundary curve.

The first sample shows how surface curves can be trimmed. This is the way trimmed surfaces are implemented in most CAD systems. The intersect curve for the base (un-trimmed) surface is first calculated and in a second step is the intersect curve trimmed.

Trimmed surface curves

The second sample shows how trimmed surfaces can be created with SUR_SPLARR. The surfaces will be approximations of the input surface.

Trimmed approx. surface

Two surfaces are created, and it should be possible to put them together with SUR_COMPOSITE. My function unfortunately fails. At the moment I do not have any program for software development, so I cannot find out why it fails.....

In some situations it is sufficient to trim surfaces as in the two samples, and it can even be a good solution.
But the best solution would be to implement bounded surfaces (Faces)! Let's hope that somebody would like to do the job. I would be happy to assist.

Sample documentation

Sample code

Execution of sample:

Download MBS code, put in mbs directory of an application, compile, start a job, create parts trim_1 and trim_2.