Elliptical (oval) stair

I just did an experiment with "Curved Ramp 10.gsm" because
I remembered that the AC 8.1 version of this object did something
strange in a SEO operation and I wanted to check the AC 10 version
to find out if it did the same thing. I placed an instance of the ramp
object in plan then drew a curved wall of about the same curvature
and length of the ramp under the ramp. I went to the 3D window
and, as expected, the wall penetrated the ramp surface. I then
performed a SEO with the wall as target and the ramp as operator
in a subtract with upward extrusion. Strangely, just like in the
8.1 version, the wall was cut but only partially. The middle portion
was cut but the part of the wall that was the beginning and the end
of the ramp were not cut.

The "Curved Ramp 10.gsm" object is made with one RULED command.
According to the GDL manual "RULED is a surface based on a
planar curve and a space curve having the same number of nodes.
Straight segments connect the corresponding nodes of the two polylines."
It is a surface only object and, indeed, if the object is cut with a section
it is hollow. So the mystery is how can a surface only object participate
in a SEO as an operator and why does the beginning and end segments
of the RULED command not cut ?

I was thinking about this because Laszlo said he could see the inside
of the TUBE which meant that either it was not a TUBE but a RULED command
or the TUBE command had been preceded by a "model surface" command.
Please see attached image
Peter Devlin

resolution problem ?

Hello David,
Yes, I had noticed that about the mask values.
I duplicated "Curved Ramp 10.gsm" and changed
the 3D script as shown in the attached image and
as you can see the wall is cut completely in the
SEO operation. Even though RULED is a surface only
command as tested with a section it does participate
in a SEO as an operator depending on the mask values.
So, go figure.
Thanks,
Peter Devlin

Hi Peter,

This is a real curiousity. The only non solid object which performs an SEO.

The object can not be solid, because the top surface of the RULED element is not planar.
Even RULED{2} can't change this. And it leads to this mess (bug).

There are many tools to script a ramp. RULED is the whorst choice.
This part no more exists. The last curved ramp uses TUBE command.

Hello Olivier
Yes, this is a real curiosity.
I remember looking at this object in 8.1
and wondering why anyone would choose
the RULED command to model a curved ramp
when there are several other commands that
do a better job. It is as though whoever wrote
this object just wanted to see if it could be done.
If you play around with the mask values you
get strange effects that don't seem to do what
you would expect. Not only is it, as you say, the
only non-solid object that performs in a SEO
but, as the manual says, it is the only GDL element
allowing the neighboring nodes to overlap.
So I guess it is just an interesting GDL anomaly.
Thanks,
Peter

Peter wrote:
So I guess it is just an interesting GDL anomaly.

Peter,

Thanks for pointing this curiosity.

A least, I had a good laugh with Dwight placing cameras inside walls. Old age is a shipwreck.
For myself, i tend to put them outside. Already that I don't have good eyes.