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Gordon
2012-08-28
2013-04-22
  • Gordon
    Gordon
    2012-08-28

    Hi trying to use program but still struggling on a few basic controls.
    1 - Having created an RCC for instance (cyc000.s) how do I change the height using MGED?
    If the height was 1mm how do I increase that to 1.5mm. (I do not wish to Kill and then redraw.)

    2 - What would be the command sequence to copy cyc000.s,  and insert the copy but change its position by rotation (by eg 35deg), about say the Z axis on the assumption that the end faces lie in the XY plane with height in the Z vector.

    3 - having created a shape Plate000.r (that is for instance a flat cylinder (faces in XY plane height in Z direction) with holes punched through it). Can I copy that shape and translate it so that the copy is displaced in the Z direction eg 10mm and rotated around the Z axis eg15deg and then possibly displaced in the Y vector by 20mm.

    Sorry if this is basic but I am struggling a lot.
    Many thanks,
    Gordon

     
  • Sean Morrison
    Sean Morrison
    2012-08-28

    Hi Gordon,

    1.  Lots of ways.

    Graphical method #1: Select Edit->Primitive Editor, type name of primitive, hit enter, adjust H value to 1.5, press Ok button.
    Graphical method #2: Select Edit->Primitive Selection, double-click primitive in list, select Edit->Set H, type "p 1.5" in command window, select Edit->Accept.
    Command-line method #1:

    e cyc000.s
    sed cyc000.s
    press "Set H"
    p 1.5
    accept

    2. Run the "clone" command.

    It'll display a helpful usage statement showing you how you can create an arbitrary number of patterned copies including copies rotated about an axis.  The sequence is one command, something like "clone -n 1 -p 100 100 100 -r  0 0 35 cyc000.s"

    3. Yes, of course. ;)

    The "cp" command will create a shallow copy of an object (so that it still references the same constituent objects).  That copy can be translated, rotated, etc, without affecting Plate000.r or the underlying objects.  The aforementioned "clone" command can also do all that except that it performs a deep copy, replicating the entire tree of Plate000.r so that your new object is completely independent.

    For what it's worth, the MGED tutorials cover most of your questions.  They're item #2 here: http://brlcad.org/wiki/Documentation
    Also, item #5 is particularly relevant for #3 as it goes into extensive detail on how to manipulate objects on the command line with the object edit "oed" command.

    Cheers!
    Sean

     
  • Sean Morrison
    Sean Morrison
    2012-08-28

    By the way, I kind of gave you the keys to the basement by suggesting the Primitive Editor for your first question.  It's a fast way to make simple edits, but be warned that it is completely unforgiving.  If you make a mistake, even a simple typo, you may irrecoverably lose the ability to do anything with that primitive.  Triple-check your changes and make a copy in case you need to undo BEFORE you hit that Ok button.

     
  • Gordon
    Gordon
    2012-08-28

    Hi Sean,
    Thanks for quick response. Will be using MGED for most part.
    Had been trying to follow method of working from Documentation page but will look tonight at tutorials on WIKI.
    As this is still a fairly early foray into the program I am still in the dark as to what the program can achieve so ask some  further question as to  whether it is possible to somehow script the creation of objects?
    Problem is:- I would like to create a series of plates (RCC) in the XY plane spaced along the Z axis that have a circular hole that is  moving out from the centre of the plate on an increasing helix about the Z axis. I can calculate the XY centre of the hole as it progresses along the Z axis and then manually enter it in for each plate but could I create a path that defines the helix intersection XY with each plate. Can I use polar coordinates? For a large number of plates (eg 110) with multiple holes entering the information by hand would be fairly time consuming.

    Not sure how clear this question is but many thanks in advance for any help you can offer'
    Gordon

     
  • Sean Morrison
    Sean Morrison
    2012-08-28

    Gordon,

    The tutorials I was originally referring to is the "Introduction to MGED" listed on the Documentation page - it's a series of about 16 tutorials that build on each other to teach some of the basic concepts.  You'll also find numerous scripting tutorials at http://brlcad.org/wiki/ under the Tutorials section that are specifically catered towards scripting the creation of objects.  BRL-CAD was made for scripting.

    There is an advanced way for performing replication along an arbitrary path via the "tracker" command, but I'm afraid it's not really got much in the way of documentation.  The pattern you describe, though, sounds very simple to script and is very similar to the existing Spiral scripting example.  You may also want to look into the graphical Build Pattern tool described in http://brlcad.org/w/images/9/9a/Principles_of_Effective_Modeling.pdf though it doesn't support helical (only spherical, cylindrical, and rectangular).

    Cheers!
    Sean

     
  • Gordon
    Gordon
    2012-08-28

    Hi Sean,
    Thanks for reply.
    Looks like I am going to be doing some reading.
    Had a look at the scripting so will have to follow the tutorials but no doubt I will be back asking some more questions at some future date.
    Many thanks,
    Gordon.

     
  • Sean Morrison
    Sean Morrison
    2012-08-28

    You're quite welcome Gordon.  Feel free to keep the questions coming, even if you think it "might" be covered by documentation somewhere.  It's a big complex system that we're working to simplify and make more discoverable, but just hearing your questions provides useful feedback and helps prioritize.

    Cheers!
    Sean