rotate_arb_face arb face pt "rx ry rz"ROTATE_ARB_FACE(nged)
NAME
rotate_arb_face - rotate a face of an ARB primitive about a fixed vertex
On this page
SYNOPSIS
DESCRIPTION
The rotate_arb_face command rotates a specified face of an ARB (arbitrary polyhedron) primitive by applying Euler rotation angles to the face’s plane normal, while keeping the face anchored at a specified vertex. The modified ARB is written back to the database.
The command requires exactly four arguments:
-
arb — The name of the ARB primitive to modify. Path prefixes are accepted; the trailing component name is used. The object must be an ARB type (ARB4–ARB8).
-
face — The face index to rotate, given as an integer from 1 to 6 (valid range depends on ARB type).
-
pt — The vertex index that serves as the fixed anchor point for the rotation, given as an integer from 1 to 8. The face’s plane is rotated about this vertex so it remains fixed in space.
-
"rx ry rz" — A single quoted string of three floating-point rotation angles in degrees (X, Y, Z Euler angles). The face normal is rotated by this amount using
bn_mat_angles, and the face’s plane equation is then re-anchored at the fixed vertex.
ARB type constraints and special cases
The command accepts all standard ARB types (ARB4, ARB5, ARB6, ARB7, ARB8). The face index and vertex index must be valid for the specific ARB type in use. There are special vertex remapping rules for degenerate ARB types:
-
ARB4: vertex indices ≥ 3 (1-indexed) are remapped to index 4 internally.
-
ARB6: vertex indices ≥ 5 are remapped to index 6 internally.
-
ARB7: if the specified face contains vertex 5, the anchor is automatically forced to vertex 5 regardless of the provided index.
After the face plane is rotated and re-anchored, all ARB vertices are recomputed from the new set of plane equations.
EXAMPLES
Example 1. Rotate face 1 of an ARB8 by 10° about vertex 1
mged> rotate_arb_face arb8.s 1 1 "10 0 0"
Rotates face 1 of arb8.s by 10° about the X axis, anchored at vertex 1. The face’s plane normal is rotated and re-anchored, and all other ARB vertices are recomputed.
Example 2. Tilt a face of an ARB6
mged> rotate_arb_face wedge.s 2 3 "0 15 0"
Rotates face 2 of the ARB6 primitive wedge.s by 15° about the Y axis, keeping vertex 3 fixed.
AUTHOR
BRL-CAD Team
BUG REPORTS
Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org