pymunk.autogeometry
Module¶
This module contain functions for automatic generation of geometry, for example from an image.
Example:
>>> import pymunk
>>> from pymunk.autogeometry import march_soft
>>> img = [
... " xx ",
... " xx ",
... " xx ",
... " xx ",
... " xx ",
... " xxxxx",
... " xxxxx",
... ]
>>> segments = []
>>> def segment_func(v0, v1):
... segments.append((tuple(v0), tuple(v1)))
>>> def sample_func(point):
... x = int(point.x)
... y = int(point.y)
... return 1 if img[y][x] == "x" else 0
>>> march_soft(pymunk.BB(0,0,6,6), 7, 7, .5, segment_func, sample_func)
>>> print(len(segments))
13
The information in segments can now be used to create geometry, for example as a Pymunk Poly or Segment:
>>> s = pymunk.Space()
>>> for (a,b) in segments:
... segment = pymunk.Segment(s.static_body, a, b, 5)
... s.add(segment)

pymunk.autogeometry.
is_closed
(polyline)[source]¶ Returns true if the first vertex is equal to the last.
Parameters: polyline ([(float,float)]) – Polyline to simplify. Return type: bool

pymunk.autogeometry.
simplify_curves
(polyline, tolerance)[source]¶ Returns a copy of a polyline simplified by using the DouglasPeucker algorithm.
This works very well on smooth or gently curved shapes, but not well on straight edged or angular shapes.
Parameters:  polyline ([(float,float)]) – Polyline to simplify.
 tolerance (float) – A higher value means more error is tolerated.
Return type: [(float,float)]

pymunk.autogeometry.
simplify_vertexes
(polyline, tolerance)[source]¶ Returns a copy of a polyline simplified by discarding “flat” vertexes.
This works well on straight edged or angular shapes, not as well on smooth shapes.
Parameters:  polyline ([(float,float)]) – Polyline to simplify.
 tolerance (float) – A higher value means more error is tolerated.
Return type: [(float,float)]

pymunk.autogeometry.
to_convex_hull
(polyline, tolerance)[source]¶ Get the convex hull of a polyline as a looped polyline.
Parameters:  polyline ([(float,float)]) – Polyline to simplify.
 tolerance (float) – A higher value means more error is tolerated.
Return type: [(float,float)]

pymunk.autogeometry.
convex_decomposition
(polyline, tolerance)[source]¶ Get an approximate convex decomposition from a polyline.
Returns a list of convex hulls that match the original shape to within tolerance.
Note
If the input is a self intersecting polygon, the output might end up overly simplified.
Parameters:  polyline ([(float,float)]) – Polyline to simplify.
 tolerance (float) – A higher value means more error is tolerated.
Return type: [(float,float)]

class
pymunk.autogeometry.
PolylineSet
[source]¶ Bases:
collections.abc.Sequence
A set of Polylines.
Mainly intended to be used for its
collect_segment()
function when generating geometry with themarch_soft()
andmarch_hard()
functions.
collect_segment
(v0, v1)[source]¶ Add a line segment to a polyline set.
A segment will either start a new polyline, join two others, or add to or loop an existing polyline. This is mostly intended to be used as a callback directly from
march_soft()
ormarch_hard()
.Parameters:  v0 ((float,float)) – Start of segment
 v1 ((float,float)) – End of segment

count
(value) → integer  return number of occurrences of value¶

index
(value[, start[, stop]]) → integer  return first index of value.¶ Raises ValueError if the value is not present.
Supporting start and stop arguments is optional, but recommended.


pymunk.autogeometry.
march_soft
(bb, x_samples, y_samples, threshold, segment_func, sample_func)[source]¶ Trace an antialiased contour of an image along a particular threshold.
The given number of samples will be taken and spread across the bounding box area using the sampling function and context.
Parameters:  bb (BB) – Bounding box of the area to sample within
 x_samples (int) – Number of samples in x
 y_samples (int) – Number of samples in y
 threshold (float) – A higher value means more error is tolerated
 segment_func (
func(v0 : Vec2d, v1 : Vec2d)
) – The segment function will be called for each segment detected that lies along the density contour for threshold.  sample_func (
func(point: Vec2d) > float
) – The sample function will be called for x_samples * y_samples spread across the bounding box area, and should return a float.

pymunk.autogeometry.
march_hard
(bb, x_samples, y_samples, threshold, segment_func, sample_func)[source]¶ Trace an aliased curve of an image along a particular threshold.
The given number of samples will be taken and spread across the bounding box area using the sampling function and context.
Parameters:  bb (BB) – Bounding box of the area to sample within
 x_samples (int) – Number of samples in x
 y_samples (int) – Number of samples in y
 threshold (float) – A higher value means more error is tolerated
 segment_func (
func(v0 : Vec2d, v1 : Vec2d)
) – The segment function will be called for each segment detected that lies along the density contour for threshold.  sample_func (
func(point: Vec2d) > float
) – The sample function will be called for x_samples * y_samples spread across the bounding box area, and should return a float.