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authorAdrian Kummerlaender2020-01-10 18:10:35 +0100
committerAdrian Kummerlaender2020-01-10 18:10:35 +0100
commit1d4b7059aa969875dbd4904c8a6980afdb39f647 (patch)
tree19846fb70330bea61947d4aadd9fe9c577466e41
parent073fe4643e0616694a3d390da6d7dcfd3af120f3 (diff)
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Implement model for local sun direction
`local_sunrise.py` renders the sky for a given time and place on earth.
-rw-r--r--local_sunrise.py67
-rw-r--r--sun.py32
2 files changed, 99 insertions, 0 deletions
diff --git a/local_sunrise.py b/local_sunrise.py
new file mode 100644
index 0000000..58ec73d
--- /dev/null
+++ b/local_sunrise.py
@@ -0,0 +1,67 @@
+import numpy as np
+import matplotlib.pyplot as plt
+from string import Template
+
+import pyopencl as cl
+from pyopencl.cltypes import make_double3
+
+mf = cl.mem_flags
+
+from planets import earth
+
+from sun import sun_direction
+from datetime import datetime
+
+config = {
+ 'size_x': 1920//4,
+ 'size_y': 1080//4,
+
+ 'ray_samples' : 16,
+ 'light_samples': 8,
+
+ 'exposure': 2.0,
+ 'zoom': 1.0,
+
+ 'eye_pos': np.array([0, 0, 1.0001]),
+ 'eye_dir': np.array([0, 1, 0]),
+
+ 'date': (2020, 1, 10),
+ 'latitude': 49.01,
+ 'longitude': 8.4
+}
+
+time_range = (5, 20, 1)
+
+cl_platform = cl.get_platforms()[0]
+cl_context = cl.Context(properties=[(cl.context_properties.PLATFORM, cl_platform)])
+cl_queue = cl.CommandQueue(cl_context)
+
+cl_picture = cl.Buffer(cl_context, mf.WRITE_ONLY, size=config['size_x']*config['size_y']*3*np.float64(0).nbytes)
+program = None
+
+with open('raymarch.cl') as f:
+ program = cl.Program(cl_context, Template(f.read()).substitute(
+ {**config, **earth}
+ )).build()
+
+for time in np.arange(*time_range):
+ pit = datetime(*config['date'], int(np.floor(time)), int((time-np.floor(time))*60), 0)
+ sun_dir = sun_direction(config['latitude'], config['longitude'], pit, 1.0)
+
+ sun = make_double3(
+ np.sin(sun_dir[1])*np.cos(sun_dir[0]),
+ np.cos(sun_dir[1])*np.cos(sun_dir[0]),
+ np.sin(sun_dir[0])
+ )
+ print(sun_dir)
+
+ program.render(
+ cl_queue, (config['size_x'], config['size_y']), None, cl_picture,
+ make_double3(*(config['eye_pos'] * earth['earth_radius'])),
+ make_double3(*(config['eye_dir'] * earth['earth_radius'])),
+ sun)
+
+ np_picture = np.ndarray(shape=(config['size_y'], config['size_x'], 3), dtype=np.float64)
+ cl.enqueue_copy(cl_queue, np_picture, cl_picture).wait();
+
+ plt.imsave("sky_%05.1f.png" % time, np_picture, origin='lower')
diff --git a/sun.py b/sun.py
new file mode 100644
index 0000000..87bc8a9
--- /dev/null
+++ b/sun.py
@@ -0,0 +1,32 @@
+import numpy as np
+from datetime import datetime
+
+## Sun direction depending on time and place
+# As described in Appendix D of "ME 4131 Thermal Environmental Engineering Laboratory Manual"
+
+def sun_declination(time):
+ day_of_year = time.timetuple().tm_yday
+ return 23.45 * np.sin(np.radians((360/365)*(284+day_of_year)))
+
+def equation_of_time(time):
+ day_of_year = time.timetuple().tm_yday
+ b = np.radians(360*(day_of_year-81)/364)
+ return 0.165*np.sin(2*b) - 0.126*np.cos(b) - 0.025*np.sin(b)
+
+def sun_direction(lat, lon, time, time_diff, summertime_shift = 0):
+ lon_std = time_diff * 15
+ clock_time = time.hour + time.minute/60
+ local_solar_time = clock_time + (1/15)*(lon - lon_std) + equation_of_time(time) - summertime_shift
+ hour_angle = 15*(local_solar_time - 12)
+
+ l = np.radians(lat)
+ h = np.radians(hour_angle)
+ d = np.radians(sun_declination(time))
+
+ altitude = np.arcsin(np.cos(l) * np.cos(h) * np.cos(d) + np.sin(l) * np.sin(d))
+ azimuth = np.arccos((np.cos(d) * np.sin(l) * np.cos(h) - np.sin(d) * np.cos(l)) / np.cos(altitude))
+
+ if (time.timetuple().tm_hour <= 12):
+ return (altitude, -azimuth)
+ else:
+ return (altitude, azimuth)