topic Re: Problem in making GDL Object in Libraries & objects

Problem in making GDL Object

Anonymous — Sun, 04 Nov 2007 18:50:40 GMT

Respected Sir,

I am facing problem in making curved back rest for the chair and oval shape table top. Since i am new in learning GDL programming and making object and working in archicad so kindly help me out to solve this. I am attaching file of chair which i was editting from Archicad library. and picture of the problem in chair.

Chair :

Gap is there when i increase the A parameter and thus back rest float in air instead of the legs.

Table :

i m able to make oval type chair from Archicads object but the supports i want to place just under table as shown in the objects.jpg

Sir i m doing reverse engineering and may my method of learning GDL is wrong so please guide me correct way. though i am familiar with all the commands. please guide me. Waiting for your reply

Regards
Deepak

Re: Problem in making GDL Object

Anonymous — Mon, 05 Nov 2007 05:29:23 GMT

Hello Deepak,
I downloaded your files and had a look at your chair object.
The issue is the geometry of circles. In this case, the definition
of the revolve object's radius derived from the "A" parameter.
The radius and center location for the revolve are right, by accident
with the default value of the "A" dimension but is wrong for all other
values of "A". If you want the seat back to follow the "A" dimension
then the "A" dimension is the chord length of the arc segment
between the vertical members of the chair back. Starting with
the chord length ("A") you need to define the arc radius and center
location for the revolve command. This math is necessary to accomplish
what you want. It is not simple and hard to explain in a post so what
I can offer is the attached .PDF which shows the derivations of the
basic variables of circle geometry. I have found this .PDF very useful.
With it you should be able to figure out how to define the parameters
of the revolve command.
Peter Devlin

Re: Problem in making GDL Object

Anonymous — Tue, 06 Nov 2007 20:19:43 GMT

Hello deepakmalhotra_131283,

Here are some ways which I have found useful when making objects and especially chairs;

- If the object is symmetrical then it pays to place the origin in the middle. Usually the chairs have the origin between the front legs. This makes mirroring parts much easier.

- Usually the TUBE is the most flexible method to make curved legs, in Your particular case the legs could have been made with POLY_ or EXTRUDE commands with much less algebra. This kind of legs could also been modeled in the plan view and then dragged to the objects 3D-code window to get the GDL written automatically. Another way is to choose the modeled parts in the plan view and then Save as... -> GDL-object. Remember to model in accordion to the true origin to get the GDL code right.

- The back rest could have easiest been made with BWALL to get the right shape. Just put RESOL big enough to get a smooth curve. I usually use 72 or so and reset the number back to 36 when the smoother resol is not needed anymore.

- The seat could have been done more flexibly with EXTRUDE

- In this case I would use the A, B , ZZYZX only as a static parameters showing the total dimensions of the object.

If You need I can post some examples.

--
Hope this helps, Juha

Re: Problem in making GDL Object

Srinivas — Thu, 08 Nov 2007 14:29:17 GMT

Hi Deepak,

Here are the two objects that we created using your pictures.

Re: Problem in making GDL Object

Anonymous — Fri, 09 Nov 2007 19:36:45 GMT

Respected Sir,

Thanks for the valuable suggestion and files and i had worket over the files and learned a lot and able to make my table with the concept similar to the given in ur file. Sir here i am attaching some of ir-regular shape chair.

Problem encountered

1) Back Rest of all chairs are curved. I did geometrically and calculated that raduis and cord length are parameter i am having but when i try to make curve using these two values it become straight line

2) How can i increase thickness of the frame in revolve command

3) How the Irregular shapes can be created so that it wont get disturbed through the change in parameters A and B and itself adjust with these parameter automatically

I feel answer to the 3rd point is by using MUL command i want to know am i thinking in a right direction.

Waiting for your reply

Regards
Deepak Malhotra

Ir-Regular shape Chairs

Anonymous — Fri, 09 Nov 2007 19:39:29 GMT

Re: Problem in making GDL Object

Anonymous — Sat, 10 Nov 2007 03:33:33 GMT

Deepak,
I did some checking and apparently you are editing a copy
of "Chair 01 10.gsm". I did some experiments on that object
and found that the curved back slats follow changes in the "A"
parameter. I would suggest that you go back to the code
in that object and simply comment out the second slat,
bring the revolve element and the cutplane forward
so that the curved slat lays in front of the vertical
chair back members and you will have approximately
what you show in your image of the chair you want.
If you study the REVOLVE command in the manual
you will understand how to increase the thickness
of the curved slat in the chair object code.
To get the shape at the end of the curved slats will
involve using a different cutting command than the
cutplane in the script. The crossing staves must be
made using additional GDL commands.
BTW double posting is considered not good form on this forum.
Peter Devlin