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Diffstat (limited to 'share/extensions/render_gears.py')
| -rwxr-xr-x | share/extensions/render_gears.py | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/share/extensions/render_gears.py b/share/extensions/render_gears.py new file mode 100755 index 0000000..00690b5 --- /dev/null +++ b/share/extensions/render_gears.py @@ -0,0 +1,165 @@ +#!/usr/bin/env python +# +# Copyright (C) 2007 Aaron Spike (aaron @ ekips.org) +# Copyright (C) 2007 Tavmjong Bah (tavmjong @ free.fr) +# +# 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 gears in SVG +""" + +from math import acos, cos, pi, radians, sin, sqrt + +import inkex +from inkex import PathElement + + +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): + f = p[0] + p = p[1:] + svgd = 'M{:.5f},{:.5f}'.format(f[0], f[1]) + for x in p: + svgd += ' L{:.5f},{:.5f}'.format(x[0], x[1]) + svgd += 'z' + return svgd + + +class Gears(inkex.GenerateExtension): + container_label = 'Rendered Gears' + + def add_arguments(self, pars): + pars.add_argument("--teeth", type=int, default=24, help="Number of teeth") + pars.add_argument("--pitch", type=float, default=20.0, help="Circular Pitch") + pars.add_argument("--angle", type=float, default=20.0, help="Pressure Angle") + pars.add_argument("--centerdiameter", type=float, default=10.0, help="Diameter of hole") + pars.add_argument("--unit", default="px", help="unit for pitch and center diameter") + + def generate(self): + teeth = self.options.teeth + pitch = self.svg.unittouu(str(self.options.pitch) + self.options.unit) + angle = self.options.angle # Angle of tangent to tooth at circular pitch wrt radial line. + centerdiameter = self.svg.unittouu(str(self.options.centerdiameter) + self.options.unit) + + # print >>sys.stderr, "Teeth: %s\n" % teeth + + two_pi = 2.0 * pi + + # Pitch (circular pitch): Length of the arc from one tooth to the next) + # Pitch diameter: Diameter of pitch circle. + pitch_diameter = float(teeth) * pitch / pi + pitch_radius = pitch_diameter / 2.0 + + # Base Circle + base_diameter = pitch_diameter * cos(radians(angle)) + base_radius = base_diameter / 2.0 + + # Diametrial pitch: Number of teeth per unit length. + pitch_diametrial = float(teeth) / pitch_diameter + + # Addendum: Radial distance from pitch circle to outside circle. + addendum = 1.0 / pitch_diametrial + + # Outer Circle + outer_radius = pitch_radius + addendum + outer_diameter = outer_radius * 2.0 + + # Tooth thickness: Tooth width along pitch circle. + tooth = (pi * pitch_diameter) / (2.0 * float(teeth)) + + # Undercut? + undercut = (2.0 / (sin(radians(angle)) ** 2)) + needs_undercut = teeth < undercut + + # Clearance: Radial distance between top of tooth on one gear to bottom of gap on another. + clearance = 0.0 + + # Dedendum: Radial distance from pitch circle to root diameter. + dedendum = addendum + clearance + + # Root diameter: Diameter of bottom of tooth spaces. + root_radius = pitch_radius - dedendum + root_diameter = root_radius * 2.0 + + half_thick_angle = two_pi / (4.0 * float(teeth)) + pitch_to_base_angle = involute_intersect_angle(base_radius, pitch_radius) + pitch_to_outer_angle = involute_intersect_angle(base_radius, outer_radius) - pitch_to_base_angle + + centers = [(x * two_pi / float(teeth)) for x in range(teeth)] + + points = [] + + for c in centers: + + # Angles + pitch1 = c - half_thick_angle + base1 = pitch1 - pitch_to_base_angle + outer1 = pitch1 + pitch_to_outer_angle + + pitch2 = c + half_thick_angle + base2 = pitch2 + pitch_to_base_angle + outer2 = pitch2 - pitch_to_outer_angle + + # Points + b1 = point_on_circle(base_radius, base1) + p1 = point_on_circle(pitch_radius, pitch1) + o1 = point_on_circle(outer_radius, outer1) + + b2 = point_on_circle(base_radius, base2) + p2 = point_on_circle(pitch_radius, pitch2) + o2 = point_on_circle(outer_radius, outer2) + + if root_radius > base_radius: + pitch_to_root_angle = pitch_to_base_angle - involute_intersect_angle(base_radius, root_radius) + root1 = pitch1 - pitch_to_root_angle + root2 = pitch2 + pitch_to_root_angle + r1 = point_on_circle(root_radius, root1) + r2 = point_on_circle(root_radius, root2) + p_tmp = [r1, p1, o1, o2, p2, r2] + else: + r1 = point_on_circle(root_radius, base1) + r2 = point_on_circle(root_radius, base2) + p_tmp = [r1, b1, p1, o1, o2, p2, b2, r2] + + points.extend(p_tmp) + + path = points_to_svgd(points) + + # Create SVG Path for gear + style = {'stroke': '#000000', 'fill': 'none', 'stroke-width': str(self.svg.unittouu('1px'))} + gear = PathElement() + gear.style = style + gear.path = path + yield gear + + if centerdiameter > 0.0: + arc = PathElement.arc((0, 0), centerdiameter / 2) + arc.style = style + yield arc + + +if __name__ == '__main__': + Gears().run() |