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support DXF bulge in old- style polylines
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@mikedh
mikedh committed Apr 24, 2019
1 parent f81f6be commit cbb4558
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258 changes: 168 additions & 90 deletions trimesh/path/exchange/dxf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -165,99 +165,29 @@ def convert_polyline(e):
# in my otherwise normal polygon", it's like SVG arc
# flags but somehow even more annoying
if '42' in e:
# from Autodesk reference:
# The bulge is the tangent of one fourth the included
# angle for an arc segment, made negative if the arc
# goes clockwise from the start point to the endpoint.
# A bulge of 0 indicates a straight segment, and a
# bulge of 1 is a semicircle.

# get the actual bulge float values
bulge = np.array(e['42'], dtype=np.float64)
# what position were vertices stored at
vid = np.nonzero(chunk[:, 0] == '10')[0]
# what position were bulges stored at in the chunk
bid = np.nonzero(chunk[:, 0] == '42')[0]

# filter out endpoint bulge if we're not closed
if not is_closed:
bid_ok = bid < vid.max()
bid = bid[bid_ok]
bulge = bulge[bid_ok]

# which vertex index is bulge value associated with
bulge_idx = np.searchsorted(vid, bid)
# use bulge to calculate included angle of the arc
angle = np.arctan(bulge) * 4.0

# the indexes making up a bulged segment
tid = np.column_stack((bulge_idx, bulge_idx - 1))

# if it's a closed segment modulus to start vertex
if is_closed:
tid %= len(lines)
# the vector connecting the two ends of the arc
vector = lines[tid[:, 0]] - lines[tid[:, 1]]
# the length of the connector segment
length = (np.linalg.norm(vector, axis=1))

# perpendicular vectors by crossing vector with Z
perp = np.cross(
np.column_stack((vector, np.zeros(len(vector)))),
np.ones((len(vector), 3)) * [0, 0, 1])
# strip the zero Z
perp = util.unitize(perp[:, :2])

# midpoint of each line
midpoint = lines[tid].mean(axis=1)

# calculate the signed radius of each arc segment
radius = (length / 2.0) / np.sin(angle / 2.0)

# offset magnitude to point on arc
offset = radius - np.cos(angle / 2) * radius

# convert each arc to three points:
# start, any point on arc, end
three = np.column_stack((
lines[tid[:, 0]],
midpoint + perp * offset.reshape((-1, 1)),
lines[tid[:, 1]])).reshape((-1, 3, 2))

# if we're in strict mode make sure our arcs
# have the same magnitude as the input data
if tol.strict:
from .. import arc as arcmod
check_angle = [arcmod.arc_center(i)['span']
for i in three]
assert np.allclose(np.abs(angle),
np.abs(check_angle))

check_radii = [arcmod.arc_center(i)['radius']
for i in three]
assert np.allclose(check_radii, np.abs(radius))

# if there are unconsumed line
# segments add them to drawing
if (len(lines) - 1) > len(bulge):
# indexes of line segments
existing = util.stack_lines(np.arange(len(lines)))
# remove line segments replaced with arcs
for line_idx in grouping.boolean_rows(
existing,
np.sort(tid, axis=1),
np.setdiff1d):
# add a single line entity and vertices
entities.append(Line(
points=np.arange(2) + len(vertices),
**polyinfo))
vertices.extend(lines[line_idx])
# add the three point arcs to the result
for arc_points in three:
entities.append(Arc(
points=np.arange(3) + len(vertices),
**polyinfo))
vertices.extend(arc_points)
# convert stupid bulge to Line/Arc entities
v, e = bulge_to_arcs(lines=lines,
bulge=bulge,
bulge_idx=bulge_idx,
is_closed=is_closed)
for i in e:
# offset added entities by current vertices length
i.points += len(vertices)
vertices.extend(v)
entities.extend(e)
# done with this polyline
return

Expand Down Expand Up @@ -478,21 +408,39 @@ def convert_text(e):
# the end of a polyline
elif polyline is not None and entity_type == 'SEQEND':
# pull the geometry information for the entity
lines = [[i['10'], i['20']]
for i in polyline[1:]]
lines = np.array([[i['10'], i['20']]
for i in polyline[1:]],
dtype=np.float64)

# check for a closed flag on the polyline
if '70' in polyline[0]:
# flag is bit- coded integer
flag = int(polyline[0]['70'])
# first bit represents closed
if bool(flag & 1):
lines.append(lines[0])
# create a single Line entity
entities.append(Line(
points=np.arange(len(lines)) + len(vertices),
**info(dict(polyline[0]))))
# add the vertices to our collection
vertices.extend(lines)
is_closed = bool(flag & 1)
if is_closed:
lines = np.vstack((lines, lines[:1]))

# get the index of each bulged vertices
bulge_idx = np.array([i for i, e in enumerate(polyline)
if '42' in e],
dtype=np.int64)
# get the actual bulge value
bulge = np.array([float(e['42'])
for i, e in enumerate(polyline)
if '42' in e],
dtype=np.float64)
# convert bulge to new entities
v, e = bulge_to_arcs(lines=lines,
bulge=bulge,
bulge_idx=bulge_idx,
is_closed=is_closed)
for i in e:
# offset entities by existing vertices
i.points += len(vertices)
vertices.extend(v)
entities.extend(e)

# we no longer have an active polyline
polyline = None
elif entity_type == 'TEXT':
Expand Down Expand Up @@ -836,6 +784,136 @@ def load_dwg(file_obj, **kwargs):
return result


def bulge_to_arcs(lines,
bulge,
bulge_idx,
is_closed=False,
metadata=None):
"""
Polylines can have "vertex bulge," which means the polyline
has an arc tangent to segments, rather than meeting at a
vertex.
From Autodesk reference:
The bulge is the tangent of one fourth the included
angle for an arc segment, made negative if the arc
goes clockwise from the start point to the endpoint.
A bulge of 0 indicates a straight segment, and a
bulge of 1 is a semicircle.
Parameters
----------------
lines : (n, 2) float
Polyline vertices in order
bulge : (m,) float
Vertex bulge value
bulge_idx : (m,) float
Which index of lines is bulge associated with
is_closed : bool
Is segment closed
metadata : None, or dict
Entitiy metadata to add
Returns
---------------
vertices : (a, 2) float
New vertices for poly-arc
entities : (b,) entities.Entity
New entities, either line or arc
"""
# make sure lines are 2D array
lines = np.asanyarray(lines, dtype=np.float64)

# metadata to apply to new entities
if metadata is None:
metadata = {}

# if there's no bulge, just return the input curve
if len(bulge) == 0:
index = np.arange(len(lines))
# add a single line entity and vertices
entities = [Line(index, **metadata)]
return lines, entities

# use bulge to calculate included angle of the arc
angle = np.arctan(bulge) * 4.0
# the indexes making up a bulged segment
tid = np.column_stack((bulge_idx, bulge_idx - 1))
# if it's a closed segment modulus to start vertex
if is_closed:
tid %= len(lines)
# the vector connecting the two ends of the arc
vector = lines[tid[:, 0]] - lines[tid[:, 1]]
# the length of the connector segment
length = (np.linalg.norm(vector, axis=1))

# perpendicular vectors by crossing vector with Z
perp = np.cross(
np.column_stack((vector, np.zeros(len(vector)))),
np.ones((len(vector), 3)) * [0, 0, 1])
# strip the zero Z
perp = util.unitize(perp[:, :2])

# midpoint of each line
midpoint = lines[tid].mean(axis=1)

# calculate the signed radius of each arc segment
radius = (length / 2.0) / np.sin(angle / 2.0)

# offset magnitude to point on arc
offset = radius - np.cos(angle / 2) * radius

# convert each arc to three points:
# start, any point on arc, end
three = np.column_stack((
lines[tid[:, 0]],
midpoint + perp * offset.reshape((-1, 1)),
lines[tid[:, 1]])).reshape((-1, 3, 2))

# if we're in strict mode make sure our arcs
# have the same magnitude as the input data
if tol.strict:
from ..arc import arc_center
check_angle = [arc_center(i)['span']
for i in three]
assert np.allclose(np.abs(angle),
np.abs(check_angle))

check_radii = [arc_center(i)['radius']
for i in three]
assert np.allclose(check_radii, np.abs(radius))

# collect new entities and vertices
entities, vertices = [], []
# add the entities for each new arc
for arc_points in three:
entities.append(Arc(
points=np.arange(3) + len(vertices),
**metadata))
vertices.extend(arc_points)

# if there are unconsumed line
# segments add them to drawing
if (len(lines) - 1) > len(bulge):
# indexes of line segments
existing = util.stack_lines(np.arange(len(lines)))
# remove line segments replaced with arcs
for line_idx in grouping.boolean_rows(
existing,
np.sort(tid, axis=1),
np.setdiff1d):
# add a single line entity and vertices
entities.append(Line(
points=np.arange(2) + len(vertices),
**metadata))
vertices.extend(lines[line_idx].copy())

# make sure vertices are clean numpy array
vertices = np.array(vertices, dtype=np.float64)

return vertices, entities


def get_key(blob, field, code):
"""
Given a loaded (n, 2) blob and a field name
Expand Down
13 changes: 13 additions & 0 deletions trimesh/path/path.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1119,6 +1119,19 @@ def area(self):
area = float(sum(i.area for i in self.polygons_full))
return area

@caching.cache_decorator
def centroid(self):
"""
Return the centroid of the path object.
Returns
-----------
centroid : (d,) float
Approximate centroid of the path
"""
centroid = self.vertices.mean(axis=0)
return centroid

@caching.cache_decorator
def length(self):
"""
Expand Down
2 changes: 1 addition & 1 deletion trimesh/version.py
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Original file line number Diff line number Diff line change
@@ -1 +1 @@
__version__ = '2.37.39'
__version__ = '2.37.40'

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