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 Component
based approach
(top) The Process
Modifying your
configuration and then repeating steps 2-4 allows
you to conduct parametric studies on a given
configuration.
(top) Geometry
Import
Tools are
available for importing both geometry from both
unstructured and structured sources. These are
summarized in the table below.
Import Tools: takes a
"finite element neutral" format triangulation and
converts it into an individual component
triangulation (which you can feed to "comp2tri" to
build a configuration). The perl script
*$CART3D/perl/fem2tri.pl" is extensively
documented.
STL:
Usage: fem2tri infile.fem > outfile.tri (top) Stereolithography
files (*STL) should be first converted to
OFF format triangulations and then converted
into Cart3D triangulations using off2tri
(below).
off2tri:
takes a "OFF
triangulation" format triangulation and converts
it into an individual component triangulation
(which you can feed to "comp2tri" to build a
configuration).The perl script
*$CART3D/perl/off2tri.pl" is extensively
documented. OFF format triangulations are
relatively common. Of particular note is that
"admesh" which is a code that tries to produce
manifold triangulations from StereoLithography
(STL) files, produces "OFF" format triangulations.
This is particularly useful for geometry
acquisition from CAD since most CAD systems now
produce *STL triangulations.
Usage: off2tri infile.fem > outfile.tri (top) tri2dat.csh:
(New! v1.5)
a simple shell script
for converting an ascii formatted Cart3D surface
triangulation to a format readable by tecplot or
paraview.
Usage: tri2dat.csh my_file.tri Produces: my_file.dat takes a "dxf
triangulation" format triangulation and converts
it into an STL triangulation.The perl script
$CART3D/perl/dxf2tri.pl is extensively documented.
DXF format triangulations are put out by autoCAD
and some other popular CAD programs.
triangulate:
Usage: dxf2STL infile.dxf > outfile
triangulate a
Multiple-grid plot3d file. Triangulate takes a
multiple-grid plot3d format configuration and
triangulates it component-by-component. Points
with duplicate geometry (same point in physical
space) are removed. It is used for converting
components specified from structured geometry
sources into intersection-ready
triangulations. Component information is retained
for each triangulation. To prevent problems
downstream, The default behavior includes
slightly (10x machine zero) perturbing vertices
which are shared between separate components. This
behavior can be suppressed with the "-n"
option. Extremely degenerate geometry can
be inflated (slightly - 10xMachineZero) around
component centers in an attempt to avoid excessive
tie-breaking down-stream. Normally the "-r"
flag is set when triangulate is run to remove
duplicate vertices from the geometry. Component
lists generated by net2p3d (or by hand)
may be fed into triangulate with the -C flag. The
output of triangulate is a
Cart3D component triangulation or a
Cart3D configuration triangulation (*.tri)
file which has a component-by-component
triangulation of the configuration, ready for
intersection.
(top)
Converts a
LaWGS net into multiple grid plot3d format. The
LaWGS format consists of any number of
structured patches with header information
between each. Currently net2p3d does not
parse scaling, translations or rotations in the
LaWGS header. When a single watertight component
is described by several meshes within the LaWGS
file, these are identified by the component number
in the LaWGS file. (In the LaWGS file, this is the
first integer following the string which is the
component's name, and comes just before the
dimensions of the network. In addition to the
multiple-grid plot3d representation of the mesh, net2p3d
outputs a (human readable) Components.list
file which describes the mapping of LaWGS networks
to component numbers. This file can be suppressed
with the "-no" option when this mapping is 1-to-1
(the default for triangulate).
Other
Auxiliary Programs
comp2tri: (New Features!)
combines any
number of individual components into a cart3d
"configuration" (generally *.tri file extension).
Original component numbers of triangles are
retained. The output of comp2tri is a Cart3D
configuration triangulation (*.tri)
file ready for intersection.
Extracts the
wetted surface of a configuration.
"Configurations" are collections of components
output either by triangulate, comp2tri, or made by
some other method. intersect is extensively
documented in AIAA 97-0197. The wetted surface
extracted by intersect is in the form of a
Cart3D wetted surface triangulation and is
watertight. Component information is
retained. By convention, output files are
generally named *.i.tri to indicate that
they are post-intersection and do not
contain any internal geometry. If "intersect" ever
fails, it drops an "Error.dat" file which is a
tecplotable file containing geometry local to the
problem which caused it to fail. One may
then view the complete geometry and overlay
the geometry contained in "Error.dat" to diagnose
the source of the problem. Intersect is quite
robust, and it begins and ends with a geometry
verification phase. If intersect stops during the
initial geometry verification it will suggest
possible problems in the input geometry
(e.g. Component N is not closed", "Component
X is non-manifold" etc These checks are
topological in nature and do not depend on
floating point math. They are therefore robust,
and I've never seen a case where they were
incorrect. In verbose mode ("-v"), this
verification phase is step #4. Try to diagnose any
geometry verification problems by viewing the
Error.dat geometry against overlaid with the input
geometry. Check in KNOWN_BUGS for a current
listing. Intersect is based on boolean
intersection predicates and uses adaptive
precision floating point math with automatic tie-breaking to
resolve degeneracies.
(top) The swiss-army knife of
triangulations: format converter, translations,
rotations and more. The default action is to convert
the input files to the extended triangulation (VTK)
format. Shape sensitivities (if present) are
automatically
adjusted to reflect any geometry manipulation. Numerical parameters can be specified as expressions using operators +, -, *, /, ^ (exponent), unary +, unary -, sqrt, exp, log, pow, sin (radians), con, tan, asin, acos, atan, atan2 (2 args), sind (degrees), cosd, tand, dasin, dacos, datan, datan2, floor, ceil, and constants pi and e. Usage: trix [-OPTIONS] [file(s) ...] Options are listed in the order they are applied: -select ... Select component(s) to mirror/scale/translate/rotate, e.g. -select 1 2 5, omit to select all Scale Geometry: -mirror %c Mirror the X, Y or Z coordinate <none> -sx %F Scale geometry in X <1.> -sy %F Scale geometry in Y <1.> -sz %F Scale geometry in Z <1.> Translate geometry: -x %F Translate geometry in x-direction <0.> -y %F Translate geometry in y-direction <0.> -z %F Translate geometry in z-direction <0.> Rotate geometry (order rx-ry-rz): -cx %F X center of rotation <0.> -cy %F Y center of rotation <0.> -cz %F Z center of rotation <0.> -rx %F Rotate geometry around x-axis (deg) <0.> -ry %F Rotate geometry around y-axis (deg) <0.> -rz %F Rotate geometry around z-axis (deg) <0.> -rg %F %F %F %F Rotate geometry around vector with tail <cx, cy, cz> and head < 0., 0., 0. > (deg) <0.> IO options: -v Be verbose <FALSE> -dp Use double precision vert-coordinates <FALSE> -o %s Output filename prefix <Components> (in VTU format) -T Output a Tecplot file for each component (.dat) -tri Output all files as traditional Cart3D tri-files -noVTK Do not write an extended triangulation (VTK) file <FALSE> Tag manipulations: -comp2gmp Overwrite or create GMPtags from component tags -tagRegion %F %F %F %F %F %F Tag rectangular region inside XMIN XMAX YMIN YMAX ZMIN ZMAX -add2comp %d Increment or decrement component tags by this amount <0> -add2gmp %d Increment or decrement GMPtags by this amount <0> Linearization: -dx Linearize with respect to x translation <FALSE> -dy Linearize with respect to y translation <FALSE> -dz Linearize with respect to z translation <FALSE> Input file list: ... file1.tri file2.triq (extensions not important) (top) diagnoseGeom:
diagnoseGeom
is a utility aimed at helping you diagnose
configuration geometries that intersect
rejects. It verifies that components in your
configuration are all valid and then performs
intersection checks on all combinations of
components in the configuration. When errors are
found, they are reported and logged into a (newly
created) subdirectory called "diagnosis". From
this information you can quickly identify the
offending component and make a repair.
Usage: diagnoseGeom [-ascii -base=basename -split -verbose] Example:
(Tell me what's wrong with the ascii
configuration triangulation "myConfig.a.tri") A Few
Technical Topics and Computational Geometry
(top)
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