How to skew something (via XFORM)

[Anonymous]

Apologies to Katarina:

Her thread was sort of hijacked into a discussion of XFORM, so I have copied it into the GDL forum for further discussion of XFORM. Her original question on walls should be answered in the remaining thread in Working in ArchiCAD:

http://archicad-talk.graphisoft.com/viewtopic.php?t=26825

Sincerely,
Karl

------------------------------

Hello,

I am trying to create a wall that is slanted in two different directions, see the picture, but I haven’t been able to figure out how to do. I have looked at the complex profiles tool, but I have only managed to create a wall that is slanted at the same direction in both ends, not in opposite directions.

Anyone who knows how to do?

Regards,
Katarina

[Karl Ottenstein]

Oleg Schmidt is the one who suggesting skewing as a practical use of XFORM:

From: 	Oleg
Subject: 	[GDLTalk] Re:  XFORM (was koordinates)
Date: 	July 13, 2001 1:33:04 PM MDT
To: 	Karl Ottenstein

Hello Karl,

This is great explanation, Karl !!!

KO> !
KO> ! This is probably not that useful for most GDL programmers

There is one opportunity which I really used in GDL practice.

It something similar SKEW. It is possible to achieve a skew in various directions.

For example:

ang=30

XFORM 1,0,0,0,

      0,1,0,0,

      TAN(ang),0,1,0

CYLIND 0.5,1

DEL 1


Thanks, Oleg

[Karl Ottenstein]

PS Glad to see the Yahoo GDL Talk messages are still present there:
http://tech.groups.yahoo.com/group/GDLTalk/messages

I never visit that forum any longer, since we have had a GDL forum here ... but I see it still has activity. I would prefer that everyone post GDL issues here, so that content is focused in just one place.

Cheers,
Karl

[Anonymous]

Hello Karl,
Your post to Laurent has the explanation text and the
math references I remember from your object but as
you say the code is not exactly the same. I suspect
that after your post to Laurent you decided to make
the lib part I described but I don't know how you made
it available to others.
Thanks Karl,
Peter Devlin