Creating L-blocks

  • Karin

    Karin - 2011-08-16

    I am trying to create a L-block using BRL-CAD. Unfortunately, I cannot attach a picture here, so I will describe it.
    A cubic's corner is cut out squarely so that the block looks like an L shape when seen from a side view and looks like a square when seen from above. I've tried using MGED but I can't figure out how to do it.
    What should I do? I would appreciate it very much if you could let me know the script(code).

  • Sean Morrison

    Sean Morrison - 2011-08-16

    You could upload a picture to and reference the URL here.

    That said, I highly recommend going through the MGED tutorial series, located on the main website under Documentation.  If you have two (arb8) blocks, you'll create a combination that subtracts the smaller from the larger.  You'll want to make sure you're smaller block is positioned properly.  You'll want to make sure you're then only drawing the new combination, not also the component shapes.

    # make bigger block
    # make smaller block positioned to make your L
    # make a combination of the two:
    comb Lshape u bigger - smaller
    # only draw the new Lshape
    e Lshape
    # look at it from an angle
    ae 35 25
    # look at it rendered

    Hope that helps some.


  • Karin

    Karin - 2011-08-18

    Thank you!!
    I uploaded it on the above address. I need to create L-block like those.
    Please let me know what I need to put in MGED. It is difficult to understand.
    I tried to follow what you have told me but something didn't work.
    So I uploaded screenshots to show you.
    Thank you so much!!!!

  • Sean Morrison

    Sean Morrison - 2011-10-27

    Those commands were near exact, but mostly notional.  As shown in the screenshot you provided, you didn't first open a geometry database.  That was implicit in my example.  You can open a new geometry database on the MGED File menu or run the "opendb" command (e.g., opendb myfile.g)

    I highly suggest going through the MGED documentation I referred to as well as it covers many if not all of the basic concepts you're needing.



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