SethTrowbridge/armature_mesher
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highly improved primitive building

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Seth Trowbridge 2026-02-28 10:41:05 -05:00
parent 84fd407c5b
commit 606df32fcb
1 changed files with 102 additions and 91 deletions
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193
__init__.py
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@ -5,35 +5,59 @@ from mathutils import Vector, Matrix
# --------------------------------------------------------------------------- # ---------------------------------------------------------------------------
# Canonical primitive builders (Z-up, origin at centre / base) # Lookup tables
# --------------------------------------------------------------------------- # ---------------------------------------------------------------------------
def _sphere_positions(radius: float, segments: int) -> list[Vector]: def _build_unit_circle(segments: int) -> list:
"""(cos, sin) sampled once per segment. Reused by all primitives."""
return [
(math.cos(2 * math.pi * i / segments),
math.sin(2 * math.pi * i / segments))
for i in range(segments)
]
def _build_latitude_stack(segments: int) -> list:
"""(sin_phi, cos_phi) for each latitude ring, poles included."""
rings = max(segments // 2, 2) rings = max(segments // 2, 2)
return [
(math.sin(math.pi * r / rings),
math.cos(math.pi * r / rings))
for r in range(rings + 1)
]
class _Tables:
"""Precomputed trig tables for a given segment count."""
def __init__(self, segments: int):
self.segments = segments
self.rings = max(segments // 2, 2)
self.circle = _build_unit_circle(segments)
self.latitudes = _build_latitude_stack(segments)
# ---------------------------------------------------------------------------
# Canonical primitive builders (Z-up, origin at centre)
# ---------------------------------------------------------------------------
def _sphere_positions(radius: float, tables: _Tables) -> list:
out = [] out = []
for r in range(rings + 1): for sin_phi, cos_phi in tables.latitudes:
phi = math.pi * r / rings for c, s in tables.circle:
sp, cp = math.sin(phi), math.cos(phi) out.append(Vector((
for s in range(segments): radius * sin_phi * c,
theta = 2.0 * math.pi * s / segments radius * sin_phi * s,
out.append(Vector((radius * sp * math.cos(theta), radius * cos_phi,
radius * sp * math.sin(theta), )))
radius * cp)))
return out return out
def _ring_positions(radius: float, segments: int) -> list[Vector]: def _ring_positions(radius: float, tables: _Tables) -> list:
"""Unit ring in the XY plane — the caller's matrix orients it.""" """Flat ring in the XY plane — caller's matrix orients it."""
out = [] return [Vector((c * radius, s * radius, 0.0)) for c, s in tables.circle]
for i in range(segments):
theta = 2.0 * math.pi * i / segments
out.append(Vector((math.cos(theta) * radius,
math.sin(theta) * radius,
0.0)))
return out
def _apply(mat: Matrix, vecs: list[Vector]) -> list[Vector]: def _apply(mat: Matrix, vecs: list) -> list:
return [(mat @ v.to_4d()).to_3d() for v in vecs] return [(mat @ v.to_4d()).to_3d() for v in vecs]
@ -41,18 +65,21 @@ def _apply(mat: Matrix, vecs: list[Vector]) -> list[Vector]:
# BMesh helpers # BMesh helpers
# --------------------------------------------------------------------------- # ---------------------------------------------------------------------------
def add_sphere(bm: bmesh.types.BMesh, mat: Matrix, radius: float, segments: int): def add_sphere(bm: bmesh.types.BMesh, mat: Matrix, radius: float, tables: _Tables):
"""Sphere built at origin/Z-up, then transformed by `mat`.""" """Sphere built at origin/Z-up, then placed by `mat`."""
rings = max(segments // 2, 2) segs = tables.segments
verts = [bm.verts.new(p) for p in _apply(mat, _sphere_positions(radius, segments))] rings = tables.rings
verts = [bm.verts.new(p) for p in _apply(mat, _sphere_positions(radius, tables))]
for r in range(rings): for r in range(rings):
for s in range(segments): for s in range(segs):
sn = (s + 1) % segments sn = (s + 1) % segs
try: try:
bm.faces.new((verts[ r * segments + s], bm.faces.new((
verts[ r * segments + sn], verts[ r * segs + s ],
verts[(r + 1) * segments + sn], verts[ r * segs + sn],
verts[(r + 1) * segments + s])) verts[(r + 1) * segs + sn],
verts[(r + 1) * segs + s ],
))
except ValueError: except ValueError:
pass pass
@ -60,40 +87,41 @@ def add_sphere(bm: bmesh.types.BMesh, mat: Matrix, radius: float, segments: int)
def add_capped_frustum(bm: bmesh.types.BMesh, def add_capped_frustum(bm: bmesh.types.BMesh,
head_mat: Matrix, head_radius: float, head_mat: Matrix, head_radius: float,
tail_mat: Matrix, tail_radius: float, tail_mat: Matrix, tail_radius: float,
segments: int): tables: _Tables):
""" """
Tapered cylinder. Each ring is built canonically in XY then placed by Tapered cylinder. Rings are built in XY then placed by per-end matrices —
the per-end matrix — no axis arithmetic at all. no axis arithmetic needed.
head_mat / tail_mat each encode: orientation (bone axes) + translation
(the head or tail world position). The ring normal naturally aligns with
the bone axis because the matrix was built that way.
""" """
head_pos = (head_mat @ Vector((0, 0, 0, 1))).to_3d() head_pos = (head_mat @ Vector((0, 0, 0, 1))).to_3d()
tail_pos = (tail_mat @ Vector((0, 0, 0, 1))).to_3d() tail_pos = (tail_mat @ Vector((0, 0, 0, 1))).to_3d()
if (tail_pos - head_pos).length < 1e-6: if (tail_pos - head_pos).length < 1e-6:
return return
hr = [bm.verts.new(p) for p in _apply(head_mat, _ring_positions(head_radius, segments))] segs = tables.segments
tr = [bm.verts.new(p) for p in _apply(tail_mat, _ring_positions(tail_radius, segments))] hr = [bm.verts.new(p) for p in _apply(head_mat, _ring_positions(head_radius, tables))]
tr = [bm.verts.new(p) for p in _apply(tail_mat, _ring_positions(tail_radius, tables))]
for i in range(segments): # Side quads
nxt = (i + 1) % segments for i in range(segs):
nxt = (i + 1) % segs
try: try:
bm.faces.new((hr[i], hr[nxt], tr[nxt], tr[i])) bm.faces.new((hr[i], hr[nxt], tr[nxt], tr[i]))
except ValueError: except ValueError:
pass pass
# Head cap
hcv = bm.verts.new(head_pos) hcv = bm.verts.new(head_pos)
for i in range(segments): for i in range(segs):
try: try:
bm.faces.new((hcv, hr[(i + 1) % segments], hr[i])) bm.faces.new((hcv, hr[(i + 1) % segs], hr[i]))
except ValueError: except ValueError:
pass pass
# Tail cap
tcv = bm.verts.new(tail_pos) tcv = bm.verts.new(tail_pos)
for i in range(segments): for i in range(segs):
try: try:
bm.faces.new((tcv, tr[i], tr[(i + 1) % segments])) bm.faces.new((tcv, tr[i], tr[(i + 1) % segs]))
except ValueError: except ValueError:
pass pass
@ -104,28 +132,25 @@ def add_capped_frustum(bm: bmesh.types.BMesh,
def _end_matrices(world_mat: Matrix, bone_matrix: Matrix, bone_length: float): def _end_matrices(world_mat: Matrix, bone_matrix: Matrix, bone_length: float):
""" """
Return (head_mat, tail_mat) — 4x4 world-space matrices for each bone end. Return (head_mat, tail_mat) — world-space matrices for each bone end.
The bone matrix (armature-local) has: The bone matrix (armature-local) columns:
col[0] = bone X axis col[0] = bone X axis
col[1] = bone Y axis ← along the bone col[1] = bone Y axis ← along the bone
col[2] = bone Z axis col[2] = bone Z axis
col[3] = head position (armature local) col[3] = head position
We want each end's matrix to have: We remap columns so our local Z = bone Y, meaning _ring_positions()
our X = bone X ← spans the cross-section ring (which lies in XY, normal = +Z) is automatically perpendicular to the
our Y = bone Z ← spans the cross-section ring bone — no cross products or acos required.
our Z = bone Y ← ring normal points along bone our X = bone X
translation = head or tail world position our Y = bone Z
our Z = bone Y (ring normal → along bone)
This means _ring_positions() (which lies in XY, normal=Z) will be
perpendicular to the bone with zero trigonometry.
""" """
bx = bone_matrix.col[0].to_3d() bx = bone_matrix.col[0].to_3d()
by = bone_matrix.col[1].to_3d() # along bone by = bone_matrix.col[1].to_3d() # along bone
bz = bone_matrix.col[2].to_3d() bz = bone_matrix.col[2].to_3d()
# 3x3 orientation: columns = [our_X, our_Y, our_Z] = [bx, bz, by]
orient = Matrix(( orient = Matrix((
(bx.x, bz.x, by.x), (bx.x, bz.x, by.x),
(bx.y, bz.y, by.y), (bx.y, bz.y, by.y),
@ -136,12 +161,8 @@ def _end_matrices(world_mat: Matrix, bone_matrix: Matrix, bone_length: float):
tail_local = head_local + by * bone_length tail_local = head_local + by * bone_length
def _make(pos_local): def _make(pos_local):
m = orient.to_4x4()
world_pos = (world_mat @ pos_local.to_4d()).to_3d()
# orientation columns also need the world rotation/scale applied
# Easiest: build full local matrix then left-multiply by world_mat.
local_mat = orient.to_4x4() local_mat = orient.to_4x4()
local_mat.col[3][:3] = pos_local # set translation in armature space local_mat.col[3][:3] = pos_local
return world_mat @ local_mat return world_mat @ local_mat
return _make(head_local), _make(tail_local) return _make(head_local), _make(tail_local)
@ -172,22 +193,22 @@ class ARMATURE_OT_build_envelope_mesh(bpy.types.Operator):
return obj is not None and obj.type == 'ARMATURE' return obj is not None and obj.type == 'ARMATURE'
def execute(self, context): def execute(self, context):
arm_obj = context.active_object arm_obj = context.active_object
original_mode = arm_obj.mode world_mat = arm_obj.matrix_world
world_mat = arm_obj.matrix_world bm = bmesh.new()
bm = bmesh.new() tables = _Tables(self.segments)
segs = self.segments
def meshify(bone_matrix, bone_length, head_radius, tail_radius, draw_head=True): def meshify(bone_matrix, bone_length, head_radius, tail_radius, draw_head=True):
head_mat, tail_mat = _end_matrices(world_mat, bone_matrix, bone_length) head_mat, tail_mat = _end_matrices(world_mat, bone_matrix, bone_length)
axis_vec = (tail_mat @ Vector((0,0,0,1))).to_3d() - (head_mat @ Vector((0,0,0,1))).to_3d()
if draw_head: if draw_head:
add_sphere(bm, head_mat, max(head_radius, 0.001), segs) add_sphere(bm, head_mat, max(head_radius, 0.001), tables)
add_sphere(bm, tail_mat, max(tail_radius, 0.001), segs) add_sphere(bm, tail_mat, max(tail_radius, 0.001), tables)
add_capped_frustum(bm, head_mat, max(head_radius, 0.001), add_capped_frustum(bm,
tail_mat, max(tail_radius, 0.001), segs) head_mat, max(head_radius, 0.001),
tail_mat, max(tail_radius, 0.001),
tables)
if original_mode == 'EDIT': if arm_obj.mode == 'EDIT':
for bone in arm_obj.data.edit_bones: for bone in arm_obj.data.edit_bones:
meshify(bone.matrix, bone.length, meshify(bone.matrix, bone.length,
bone.head_radius, bone.tail_radius, bone.head_radius, bone.tail_radius,
@ -198,9 +219,6 @@ class ARMATURE_OT_build_envelope_mesh(bpy.types.Operator):
bone.bone.head_radius, bone.bone.tail_radius, bone.bone.head_radius, bone.bone.tail_radius,
bone.parent is None) bone.parent is None)
if original_mode != 'OBJECT':
bpy.ops.object.mode_set(mode='OBJECT')
mesh = bpy.data.meshes.new(arm_obj.name + "_envelope_mesh") mesh = bpy.data.meshes.new(arm_obj.name + "_envelope_mesh")
bm.to_mesh(mesh) bm.to_mesh(mesh)
bm.free() bm.free()
@ -209,18 +227,6 @@ class ARMATURE_OT_build_envelope_mesh(bpy.types.Operator):
result_obj = bpy.data.objects.new(arm_obj.name + "_envelope", mesh) result_obj = bpy.data.objects.new(arm_obj.name + "_envelope", mesh)
context.collection.objects.link(result_obj) context.collection.objects.link(result_obj)
bpy.ops.object.select_all(action='DESELECT')
result_obj.select_set(True)
context.view_layer.objects.active = result_obj
if original_mode == 'EDIT':
result_obj.select_set(False)
arm_obj.select_set(True)
context.view_layer.objects.active = arm_obj
bpy.ops.object.mode_set(mode='EDIT')
source_label = {'OBJECT': "rest pose", 'POSE': "current pose", 'EDIT': "edit-bone layout"}.get(original_mode, original_mode)
self.report({'INFO'}, f"Created '{result_obj.name}' from {source_label}.")
return {'FINISHED'} return {'FINISHED'}
@ -237,8 +243,11 @@ class VIEW3D_PT_armature_mesher(bpy.types.Panel):
def draw(self, context): def draw(self, context):
layout = self.layout layout = self.layout
op = layout.operator(ARMATURE_OT_build_envelope_mesh.bl_idname, op = layout.operator(
text="Build Envelope Mesh", icon='OUTLINER_OB_MESH') ARMATURE_OT_build_envelope_mesh.bl_idname,
text="Build Envelope Mesh",
icon='OUTLINER_OB_MESH',
)
op.segments = 16 op.segments = 16
@ -249,10 +258,12 @@ class VIEW3D_PT_armature_mesher(bpy.types.Panel):
classes = (ARMATURE_OT_build_envelope_mesh, VIEW3D_PT_armature_mesher) classes = (ARMATURE_OT_build_envelope_mesh, VIEW3D_PT_armature_mesher)
def register(): def register():
for cls in classes: bpy.utils.register_class(cls) for cls in classes:
bpy.utils.register_class(cls)
def unregister(): def unregister():
for cls in reversed(classes): bpy.utils.unregister_class(cls) for cls in reversed(classes):
bpy.utils.unregister_class(cls)
if __name__ == "__main__": if __name__ == "__main__":
register() register()