NASTRAN-G(1)

🌸 NASTRAN-G(1) — the BRL-CAD girlie's guide to NASTRAN-G 🌸

okay so bestie, you found the nastran-g page in the BRL-CAD manual set, and honestly? it's a whole vibe. let's get into it 💅

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✨ NAME ✨

nastran-g — converts a NASTRAN finite element model into a BRL-CAD database, no cap 🫶

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✨ SYNOPSIS ✨

nastran-g [-n] [-m] [-t tolerance] [-x lvl] [-X lvl] [-i nastran_file] -o database.g

like, that's the whole shape of it. flags flagging, files filing 💖

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✨ DESCRIPTION ✨

okay so here's the tea 🍓 — nastran-g reads a NASTRAN bulk data deck and converts all the geometry it describes into a BRL-CAD database.g file. input comes from the file you name with -i, or from standard input if you don't give -i at all. conversion kicks off at the BEGIN BULK card — everything before that? ignored, not her problem, we don't see it 👑.

now, lowkey important: only a subset of NASTRAN element types is handled. like, she's talented but she's not doing everything:

• CROD and CBAR elements become right circular cylinders (RCC) — the radius is derived from the referenced PBAR cross-sectional area, iykyk 🌈
• CTRIA3 and CQUAD4 shell elements get tessellated into surfaces ✨
• grid points (GRID), coordinate systems (CORD1/CORD2), and properties (PBAR, PSHELL, BAROR) are interpreted as needed 🧚

all geometry is transformed into the default Cartesian coordinate system. the resulting primitives get grouped into combinations: pbars, shells, and a top-level all 💜

by default, the shell elements are written as bot(5) (BOT) solids, and the model is assumed to be in inches 📏

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✨ OPTIONS ✨

• -n — write surfaces created from CQUAD4 and CTRIA3 elements as NMG solids instead of the default BOT solids. the NMG glow-up 💅
• -m — treat the NASTRAN input as millimeters rather than the default inches. metric girlies rise 🦋
• -t tolerance — set the distance tolerance, in millimeters: two vertices closer than this are treated as the same vertex. defaults to the BRL-CAD distance tolerance. tiny number, big consequences ✨
• -x lvl — set the librt debug flags to the given hexadecimal value. hex girlies, this one's for you 🔥
• -X lvl — set the NMG debug flags to the given hexadecimal value. yes it's a capital X, no they're not the same flag, don't @ me 💀
• -i nastran_file — read the NASTRAN bulk data deck from nastran_file instead of standard input 📂
• -o database.g — write the converted geometry to database.g. defaults to nastran.g. (but like, always pass -o, be intentional 🎀)

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✨ EXAMPLES ✨

Example 1. Convert a metric model and inspect the result 👑

nastran-g -m -i wing.nas -o wing.g
mged wing.g 'tops'

converts the millimeter NASTRAN deck wing.nas to wing.g, then lists the top-level objects with mged(1) so the all combination can be drawn and examined. look at her go 😭💖

Example 2. Convert from a pipeline using NMG shells and a tightened tolerance 🌀

cat model.bdf | nastran-g -n -t 0.005 -o model.g

reads the bulk data deck from standard input, writes shell elements as NMG solids, and treats vertices within 0.005 mm of each other as coincident. pipeline + tight tolerance = main character energy fr fr ⭐

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✨ SEE ALSO ✨

brlcad(1), mged(1), bot(5) — go read those too, they're icons 🌸

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✨ AUTHOR ✨

BRL-CAD Team 🫶

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✨ COPYRIGHT ✨

This software is Copyright (c) 1998-2026 by the United States Government as represented by U.S. Army Research Laboratory.

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✨ BUG REPORTS ✨

reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org 📧 found a bug? tell the devs, don't suffer in silence bestie 🙈

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and that's the page!! brought to you by the BRL-CAD crew — NASTRAN-G(1), BRL-CAD, and don't forget the date gang, go off 💜✨🎀