Revision: 4693
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=4693&view=rev
Author: mdboom
Date: 2007-12-10 11:46:00 -0800 (Mon, 10 Dec 2007)
Log Message:
-----------
Numpify arc/wedge approximation.
Modified Paths:
--------------
branches/transforms/lib/matplotlib/path.py
Modified: branches/transforms/lib/matplotlib/path.py
===================================================================
--- branches/transforms/lib/matplotlib/path.py 2007-12-10 16:27:25 UTC (rev
4692)
+++ branches/transforms/lib/matplotlib/path.py 2007-12-10 19:46:00 UTC (rev
4693)
@@ -408,10 +408,14 @@
unit_circle = classmethod(unit_circle)
[EMAIL PROTECTED]
- def arc(cls, theta1, theta2, is_wedge=False):
+ def arc(cls, theta1, theta2, is_wedge=False, n=None):
"""
Returns an arc on the unit circle from angle theta1 to angle
theta2 (in degrees).
+
+ If n is provided, it is the number of spline segments to make.
+ If n is not provided, the number of spline segments is determined
+ based on the delta between theta1 and theta2.
"""
# From Masionobe, L. 2003. "Drawing an elliptical arc using
# polylines, quadratic or cubic Bezier curves".
@@ -422,7 +426,7 @@
theta1 *= math.pi / 180.0
theta2 *= math.pi / 180.0
- twopi = math.pi * 2.0
+ twopi = math.pi * 2.0
halfpi = math.pi * 0.5
eta1 = math.atan2(math.sin(theta1), math.cos(theta1))
@@ -432,7 +436,8 @@
eta2 += twopi
# number of curve segments to make
- n = int(2 ** math.ceil((eta2 - eta1) / halfpi))
+ if n is None:
+ n = int(2 ** math.ceil((eta2 - eta1) / halfpi))
deta = (eta2 - eta1) / n
etaB = eta1
@@ -450,7 +455,9 @@
codes = Path.CURVE4 * npy.ones((length, ), Path.code_type)
vertices[1] = [xB, yB]
codes[0:2] = [Path.MOVETO, Path.LINETO]
+ codes[-2:] = [Path.LINETO, Path.CLOSEPOLY]
vertex_offset = 2
+ end = length - 2
else:
length = n * 3 + 1
vertices = npy.zeros((length, 2), npy.float_)
@@ -458,32 +465,31 @@
vertices[0] = [xB, yB]
codes[0] = Path.MOVETO
vertex_offset = 1
+ end = length
t = math.tan(0.5 * deta)
alpha = math.sin(deta) * (math.sqrt(4.0 + 3.0 * t * t) - 1) / 3.0
- for i in xrange(n):
- xA = xB
- yA = yB
- xA_dot = xB_dot
- yA_dot = yB_dot
+ steps = npy.linspace(eta1, eta2, n + 1, True)
+ cos_eta = npy.cos(steps)
+ sin_eta = npy.sin(steps)
- etaB += deta
- cos_etaB = math.cos(etaB)
- sin_etaB = math.sin(etaB)
- xB = cos_etaB
- yB = sin_etaB
- xB_dot = -sin_etaB
- yB_dot = cos_etaB
+ xA = cos_eta[:-1]
+ yA = sin_eta[:-1]
+ xA_dot = -yA
+ yA_dot = xA
- offset = i*3 + vertex_offset
- vertices[offset:offset+3] = [
- [xA + alpha * xA_dot, yA + alpha * yA_dot],
- [xB - alpha * xB_dot, yB - alpha * yB_dot],
- [xB, yB]]
+ xB = cos_eta[1:]
+ yB = sin_eta[1:]
+ xB_dot = -yB
+ yB_dot = xB
- if is_wedge:
- codes[-2:] = [Path.LINETO, Path.CLOSEPOLY]
+ vertices[vertex_offset :end:3, 0] = xA + alpha * xA_dot
+ vertices[vertex_offset :end:3, 1] = yA + alpha * yA_dot
+ vertices[vertex_offset+1:end:3, 0] = xB - alpha * xB_dot
+ vertices[vertex_offset+1:end:3, 1] = yB - alpha * yB_dot
+ vertices[vertex_offset+2:end:3, 0] = xB
+ vertices[vertex_offset+2:end:3, 1] = yB
return Path(vertices, codes)
arc = classmethod(arc)
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