Read and Write SG Data#

Every format goes through one in-memory object. sgio.read() loads a solver or mesh file into a sgio.StructureGene; sgio.write() emits one.

        flowchart LR
    subgraph IN ["Input"]
        direction TB
        VABS_I["VABS<br/>.sg"]
        SC_I["SwiftComp<br/>.sg"]
        ABQ_I["Abaqus<br/>.inp"]
        GMSH_I["SG manifest<br/>.sg.json + .msh"]
    end

    SG(["StructureGene"])

    subgraph OUT ["Output"]
        direction TB
        VABS_O["VABS<br/>.sg"]
        SC_O["SwiftComp<br/>.sg"]
        ABQ_O["Abaqus<br/>.inp"]
        GMSH_O["Gmsh<br/>.msh"]
        VTK_O["VTK / VTU<br/>.vtk .vtu"]
    end

    VABS_I -- "read" --> SG
    SC_I -- "read" --> SG
    ABQ_I -- "read" --> SG
    GMSH_I -- "read" --> SG

    SG -- "write" --> VABS_O
    SG -- "write" --> SC_O
    SG -- "write" --> ABQ_O
    SG -- "write" --> GMSH_O
    SG -- "write" --> VTK_O

VTK and VTU are write-only, mesh-only export targets. A bare .msh carries no material data, so Gmsh input is read through an SG manifest — see Prepare a Gmsh Mesh for SG Conversion.

sgio.convert() chains a read and a write in one call; see Convert SG Data.

Read#

import sgio

sg = sgio.read(
    'airfoil.sg',
    file_format='vabs',
    model_type='BM2',
    format_version='4.1',
)

file_format and model_type identifiers are listed in Formats and Model Types. sgdim, model_type and, for a 1D/2D SG, model_space may be omitted only when the format implies them — a VABS file defines all three. Abaqus input requires them:

sg = sgio.read('cube.inp', file_format='abaqus', model_type='SD1', sgdim=3)

Write#

import sgio

sgio.write(sg, 'cross_section.sg', file_format='vabs', format_version='4.1')

Node and element IDs are renumbered automatically when the target format requires it, with a warning.

A SwiftComp input also needs omega, the SG’s measure over the dimensions it shares with the macro model. It is computed from the SG bounding box unless sg.omega is set; see the omega table in Formats and Model Types. To give it by hand, pass omega to sgio.read (stored on the SG) or to sgio.write (used for that write only, leaving sg unchanged):

sgio.write(sg, 'weave.sc', file_format='sc', omega=44.54)

Writing is atomic: the target file is replaced only once the whole file has been written, so a failure part way through leaves any existing file intact.

Pass mesh_only=True to write geometry without materials or analysis configuration — useful for visualization targets:

sgio.write(sg, 'visualization.msh', file_format='gmsh', mesh_only=True)

Full signatures are in I/O Functions.

See Also#