Name
g-nmg — Perform Boolean evaluations to produce NMG objects
Synopsis
g-nmg [-v ] [-b ] [-xX lvl] [-t calc_dist_tol] [-a abs_tess_tol] [-n norm_tess_tol] [-P number_of_CPUs] [-r rel_tess_tol] [-o outfile.g] infile.g object(s)
DESCRIPTION
g-nmg
performs the Boolean operations in the specified
object(s)
and writes the resulting NMG primitives (or BOT primitives, if the
-b
option is specified) to
outfile.g
or to
stdout
if the
-o
option is not used.
The following options are available:
-a abs_tess_tolSpecify an absolute tessellation tolerance (in millimeters). This requires that the maximum absolute error from the tessellated surface to the actual surface must not be greater than abs_tess_tol.
-bConvert the results to a BOT primitive (triangle representation) instead of leaving it as an NMG.
-n norm_tess_tolSpecify a surface normal error tolerance (in degrees) for the tessellation.
-P #_of_CPUsSpecify the number of CPUs.
-o outfile.gSpecify the name of the file to be created. This should not be the same as the input file.
-r rel_tess_tolSpecify a relative error tolerance. This effectively sets an absolute tolerance for each primitive solid by multiplying the overall size of the solid by rel_tess_tol. This allows small objects to be tessellated with small tolerances, while large objects are tessellated with large tolerances. For example, specifying
-r 0.1when tessellating an object 2m in size will result in a tolerance of .2m (2.0 * 0.1). The same option will cause a 5cm object to be tessellated with a tolerance of 0.5cm.-t calc_dist_tolSpecify a calculational distance tolerance (in millimeters). This tolerance is used to distinguish neighboring vertices. Any two vertices less than this tolerance distance apart will be considered the same vertex. The default value is 0.005mm. Prior to performing the Boolean operations for each region, the involved primitive solids are converted to a planar facetted approximation and stored as NMG solids. This tessellation can be controlled using the tessellation tolerances.
-vProduce copious progress information.
-xSet librt debug flags. The definitions of these flags may be found in raytrace.h.
-XSet NMG routines debug flags. The definitions of these flags may be found in h/nmg.h.
BUGS
Boolean operations under finite precision arithmetic are not guaranteed to be solvable. As a result this command can fail. Scaling geometry adjusting tolerance values, and restructuring the boolean tree will often result in a successful tessellation.
