A few questions about CUTPOLYA and CUTFORM

[Anonymous]

Hello,
I have never understood what the meaning
of the status values are in the CUTPOLYA and CUTFORM commands.

For CUTPOLYA the manual says:

status: controls the treatment of the generated cut polygons
1: use the attributes of the body for the generated polygons
and edges.
2: generated cut polygons will be treated as normal polygons.

For CUTFORM the manual says:

j1: use the attributes of the body for the generated polygons
and edges
j2: generated cut polygons will be treated as normal polygons

In the CUTPOLYA command you have a choice either one or two.
In the CUTFORM command you can set both independently and
if you set one to zero you can get some strange effects
like the cut surface becomes transparent.

(edit) Actualy what happens is if j2 is set to zero then the object
becomes hollow, some surfaces become transparent, and
some surfaces dissapear.

Is the "body" the cutting body or the body being cut ?
What is a "normal polygon" and as opposed to what ?
In the CUTPOLYA command what is the difference
between setting the status to one or two ?
I have never seen a difference in how the cut body looks
after setting the status one way and then the other.

In the CUTFORM command j1 and j2 seem be alternative
like in the CUTPOLYA but apparently not because they
are independent values unlike CUTPOLYA.

After all these years of wondering it would
be great if someone could explain these things to me.

Thank you,
Peter Devlin

[Laszlo Nagy]

This is a guess so you need to try it:
I think this can be important if you define a different Pen and/or Material in the script just before performing the CUTPOLY or CUTFORM operation.
Depending on the value of the status code, the cut surfaces and the edges of the cut surfaces will appear using the pen and material of the cut body or the pen and material defined just before the CUTPOLY or CUTFORM command.

I hope this is it, I have no other idea.

[Frank Beister]

I have not the time in the moment to translate the entries on selfgdl.com. But you are right Laszlo for the flag j1. The second j2 is important for AC10, when PROJECT2{3} can differ between surfaces, which are cut and which are "normal" (uncut) ones. It has no influence on the 3D appearance but for the 2D projection.
The body is the body resulting out of the cutting process. All surface, which are generated by CUTPOLY/CUTFORMA get either their own attributes or the ones, which are set in the moment before the cut defined.
I have made some demonstration objects for this. They are not available at selfgdl yet, but I have a look and will post it here, if I find something enlightening. 😉

[Anonymous]

Hello, Frank and Laszlo,
I thank you both for posting back.

Laszlo, you are saying that the status code f1 controls whether
the cut surfaces of the body being cut will have the material and pen
defined for the wrest of the cut body or the material and pen
of the cutting body, similar to the choice for SEO.
I will have to experiment because I have
never wanted the the cut surface to be different from the
the wrest of the cut object.

Frank, have you seen the strange effect I described when
f2 is set to zero ? This is seen in the Section/Elevation window
when the object is cut by a section line. See image below.
I will have to see what you mean about the consequence
of alternate f2 settings on the PROJECT2{3} command.

Do the two of you agree that a "normal" polygon is an uncut polygon
and therefor a non-normal polygon is a cut polygon ?

Thank you,
Peter Devlin