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shade.py
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shade.py
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#!/usr/bin/python
# Copyright 2007-2010 Brandon Stafford
#
# This file is part of Pysolar.
#
# Pysolar 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 3 of the License, or
# (at your option) any later version.
#
# Pysolar 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 Pysolar. If not, see <http://www.gnu.org/licenses/>.
"""Shade calculation functions
"""
import math
def GetSideByLawOfCosines(side_a, side_b, included_angle_deg):
return math.sqrt(pow((side_a), 2) + pow(side_b, 2) - (2 * side_a * side_b * math.cos(math.radians(included_angle_deg))))
def GetXShade(width, x_spacing, azimuth_deg):
n = GetSideByLawOfCosines(width/2, x_spacing, azimuth_deg)
p = (width/2) * math.sin(math.radians(azimuth_deg))
theta_deg = math.degrees(math.asin(p/n))
alpha_deg = azimuth_deg + theta_deg
d = GetSideByLawOfCosines(width/2, n, alpha_deg)
gamma_deg = math.degrees(math.asin((n * math.sin(math.radians(alpha_deg)))/d))
shaded_width = d * math.cos(math.radians(gamma_deg))
if(pow(d, 2) + pow(width/2, 2) < pow(n, 2)): # check for obtuse triangle
shaded_width = 0
#print "theta in deg:", theta_deg, "gamma in deg:", gamma_deg, "shaded width:", shaded_width
return min(shaded_width, width)
def GetYShade(height, y_spacing, altitude_deg):
return GetXShade(height, y_spacing, 90 - altitude_deg)