A torus face covering most of its tube off the tube's quarter lines (an
exhaust collector's bend: 326° of the tube from −113.8°) needed a fifth
quarter along the tube, which STEP counts from the outer equator: its form
ran past a full turn of the tube and SMLib refused the solid. #8496 turns
frames about the axis only, and the torus label had no tube reference.
The torus label gets a tube start (`tube_start`, radians; 0 and left out
of the record by default, so older records mean what they did): v counts
from there, in every evaluator, form, pcurve, iso curve, tessellation,
placement, SSI and SMLib transfer. A spilling torus face's tube start moves
to where its tube begins, or a turn before where it ends, whichever puts
its tube circles on the grid of a round face they are about the axis of
(a pipe's cylinder meeting the bend); circles round the tube are labelled
from the tube start (brep::form::on_tube), so their forms and pcurves lie
on the face's quarter grid exactly. The saved-format change is one file,
crates/doc/src/format/pending/torus-tube-start.rs.
Engine assembly: COLLECTOR_EXHAUST_VER_1 now comes in as a closed solid
(refused 3 -> 2); Poppy Humanoid unchanged (4).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Every SMLib analytic surface is a B-spline surface, and its trims are in that NURBS's
parameters. Face::nurbs keeps that NURBS: the face's domain and pcurves are its (u, v), and
`surface` says what the face is. Face::parameters is the surface every (u, v) evaluation uses.
The SMLib conversion reads and writes it (fork FACE_NURBS_FORM, SMLIB_REV c4483f6); the STEP
writer writes the analytic surface and the face's edges without pcurves.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt
write::topology::layout says which shells make each solid (a material region's outer shell
and its voids) and which are sheets, and outer_loop which loop of a face is its outer one;
the STEP writer uses both, and the IGES writer can too.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt
A placed revolution is written exactly whenever its placement maps revolutions about the
axis onto revolutions (one scale across the axis, another along it, then a rotation or
reflection), its profile placed with it; a conic profile stays a conic under a similarity.
A void's CLOSED_SHELL keeps the record's sides (normals out of the material, into the void)
through an ORIENTED_CLOSED_SHELL .T., as SolidCraft has written voids. Reader::frame reads an
assembly placement (AXIS2_PLACEMENT_3D, or _2D in the XY plane).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt
write::topology writes each material region as a MANIFOLD_SOLID_BREP (BREP_WITH_VOIDS
with its voids as ORIENTED_CLOSED_SHELLs), open shells as a SHELL_BASED_SURFACE_MODEL,
faces as ADVANCED_FACEs on their exact surface with FACE_OUTER_BOUND/FACE_BOUND of
EDGE_LOOPs and VERTEX_LOOPs, edges as EDGE_CURVEs on their exact curve over the record's
interval, and the record's exact pcurves as PCURVEs of SURFACE_CURVE/SEAM_CURVE. A record
surface's (u, v) map linearly onto STEP's (planes on their orthonormal frame, narrowing
cones turned over, revolutions angle first), and pcurves go through the same map.
Writer::add_distinct writes topology entities unshared. topology::Solid lists the faces
the reader turned over (their loops disagree with their same_sense).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt
jyviko