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#!/usr/bin/env python
#
# Copyright (C) 2013 Brett Graham (hahahaha @ hahaha.org)
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#
"""
Generate a gear rack as SVG.
"""
from math import acos, cos, radians, sin, sqrt, tan
import inkex
def involute_intersect_angle(Rb, R):
Rb, R = float(Rb), float(R)
return (sqrt(R ** 2 - Rb ** 2) / Rb) - (acos(Rb / R))
def point_on_circle(radius, angle):
x = radius * cos(angle)
y = radius * sin(angle)
return x, y
def points_to_svgd(p):
"""
p: list of 2 tuples (x, y coordinates)
"""
f = p[0]
p = p[1:]
svgd = 'M{:.3f},{:.3f}'.format(f[0], f[1])
for x in p:
svgd += 'L{:.3f},{:.3f}'.format(x[0], x[1])
return svgd
class RackGear(inkex.GenerateExtension):
container_label = 'Rendered Gear Rack'
def add_arguments(self, pars):
pars.add_argument("--length", type=float, default=100.0, help="Rack Length")
pars.add_argument("--spacing", type=float, default=10.0, help="Tooth Spacing")
pars.add_argument("--angle", type=float, default=20.0, help="Contact Angle")
def generate(self):
length = self.svg.unittouu(str(self.options.length) + 'px')
spacing = self.svg.unittouu(str(self.options.spacing) + 'px')
angle = radians(self.options.angle)
# generate points: list of (x, y) pairs
points = []
x = 0
tas = tan(angle) * spacing
while x < length:
# move along path, generating the next 'tooth'
points.append((x, 0))
points.append((x + tas, spacing))
points.append((x + spacing, spacing))
points.append((x + spacing + tas, 0))
x += spacing * 2.
path = points_to_svgd(points)
# Create SVG Path for gear
style = {'stroke': '#000000', 'fill': 'none', 'stroke-width': str(self.svg.unittouu('1px'))}
yield inkex.PathElement(style=str(inkex.Style(style)), d=str(path))
if __name__ == '__main__':
RackGear().run()
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