SWEEPX, LOFTX, SSBS (SliceSolidBySurface) commands to SWEEP,LOFT Solids+Surfaces, Slice Solids by Su

Sakko · December 2011

Hi Bricscad Users,

I am doing conceptual architectural modeling and "in-house" programming and customization of DWG CAD programs. In the course of this work, I make intensive use of 3D solids and Surfaces.

My path is mostly to use Lisp and C#.NET in combination, exposing the .NET functionality missing from Lisp to the Lisp environment and command line, using "LispFunction" and "CommandMethod" Attributes respectively. I have exposed most of the SWEEP and LOFT C#.NET functionality of the .NET API of Bricscad V12 in 2 commands .

I am programming in a "as the need arises", "on the fly" non commercial modus and therefore I have not implemented rigorous testing and validation in the SWEEPX , LOFTX and SSBS (SliceSolidBySurface) commands nor have I written a detailed documentation.

The only validation and messages are the built-in ones (e.g. Skin path intersections with profiles are not monotonic ) coming from Bricscad and Teigha ACIS Libs.

Self-intersecting Solids and Surfaces are NOT checked or disabled;

They are possible and artistic !

Due to this fact 6 Basic Rules are important :

Use Closed OR Open Planar Curves as Loft and Sweep Profile-Curves /Cross Sections

Use Closed OR Open Planar or non-planar Curves as Loft / Sweep Paths
Use Open Planar or non-planar Curves as Loft Guides
Never use mixed Closed and Open Profile-Curves /Cross Sections for a Sweep or Loft operation
Use Open Profile-Curves /Cross Sections for Surfaces ONLY. If you choose to create Solids, it will be an inconsistent Solid not capable of Boolean Operations.
Use Closed OR Open Profile-Curves /Cross Sections for Solids

I think their use is self-explanatory at the command line of Bricscad !

For more explanation consult the documentation of programs having already these commands

I have used the names SWEEPX and LOFTX to avoid interference with other commands and applications !

Command SWEEPX

The command creates a 3Dsolid or SweptSurface (ACIS) by sweeping an open or closed, planar (non-planar NOT at this time ,but I don't know why it doesn't work) curve along an open or closed path curve. Open curves create surfaces and closed curves create solids or surfaces, according to your choice !

I have included all the SweepOptions mostly used like Alignment, Basepoint, Scale and Twist, although Scale and Twist don't seem to have any effect or impact on the Sweep operation. Propably a bug or not yet properly exposed to .Net ???

The Bank option , whether the curve(s) being swept will naturally rotate along a 3D sweep path (3D polyline, spline) is also not working ????? and I have not exposed it to the user; Bank = false is used.

Command Sequence :

: sweepx

Sweep a SOlid or a SUrface? [SOlid/SUrface] : : su

Select profile-curves (Regions or Planar Curves) to SWEEP:

Entities in set: 1

Select profile-curves (Regions or Planar Curves) to SWEEP:

Select path along which to sweep:

Enter an Option [Alignment/Basepoint/Scale/Twist]: b

Select Basis Point for the sweep:

Enter an Option [Alignment/Basepoint/Scale/Twist]:

DONE !

Command LOFTX

This command Creates a 3Dsolid or LoftedSurface (ACIS) thus filling the space between several cross sections using optionally any number of Guides or a single Loft Path.

I have included all the LoftOptions mostly used like Ruled, Smooth fit, Closed, No normal, Normal to all sections, Normal to start section, Normal to end section, Normal to start+end sections. All seem to work properly...still testing !

Draft Angles come in the near future...

The option Closed needs at least 3 Cross Sections /Curves !

The reason for that is left to you as homework .......

This option connects the first and the last Loft profile (cross section) thereby creating

a closed Surface or 3Dsolid like a Torodial (Torus) !

If Guides are used then following Rules must be followed :

· Every Guide must intersect each cross section curve (profile)

· Every Guide starts on the first cross section curve (profile)

· Every Guide ends on the last cross section curve (profile)

Command Sequence :

: LOFTX

Loft a SOlid or a SUrface? [SOlid/SUrface] : su