sphgroup gname target_sphere.sSPHGROUP(nged)
NAME
sphgroup - create a group of all regions whose centers fall inside a sphere
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SYNOPSIS
DESCRIPTION
The sphgroup command creates a new combination gname containing all regions in the database whose bounding-box center point lies within the bounding sphere defined by target_sphere.s. The sphere argument must be an existing ELL or SPH primitive in the database.
The command scans all regions in the database (objects flagged as regions) and computes each region’s axis-aligned bounding box. A region is included in gname if the center of its bounding box is within or on the surface of target_sphere.s — specifically, if the distance from the bounding-box center to the sphere’s center vertex is less than or equal to the sphere’s radius. Non-region objects, hidden objects, and the sphere primitive itself are skipped.
All qualifying regions are added to gname as union (u) members with no item ID or air code set. If gname does not already exist it is created; if it does exist, the new members are appended to it.
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Note
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The containment test uses the center of each region’s bounding box, not all eight corners. A region whose center is outside the sphere is excluded even if part of its geometry overlaps the sphere. |
EXAMPLES
Example 1. Group all regions centered inside a sphere primitive
mged> sphgroup cluster.c search_sphere.s
Creates the combination cluster.c containing all regions whose bounding-box centers lie within the sphere primitive search_sphere.s. The sphere search_sphere.s must already exist in the database and must be an ELL or SPH primitive.
Example 2. First create the bounding sphere, then group
mged> make search_sphere.s sph mged> sphgroup nearby.c search_sphere.s
Creates a unit sphere at the origin with make, then groups all regions centered within it into nearby.c.
AUTHOR
BRL-CAD Team
BUG REPORTS
Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org