add sky discretisation tools for producing simplified sky maps

src/alinea/astk/sky_map.py

@@ -35,6 +35,46 @@ def _c(x):
     az_c, z_c = numpy.meshgrid(_c(azimuth), _c(zenith))
     return azimuth, zenith , az_c, z_c
 
+def sky_dirs(d_az=10, d_z=10, n_az=None, n_z=None):
+    _,_,az, z = sky_grid(d_az=d_az, d_z=d_z, n_az=n_az, n_z=n_z)
+    return [*zip(90 - z.flatten(), az.flatten())]
+
+def sun_path(sky_irradiance):
+    irr = sky_irradiance
+    return [*zip(irr.sun_elevation, irr.sun_azimuth)]
+
+
+def sky_turtle(sectors=46):
+    # Hierarchical direction from tutle.xls file of J Dauzat
+    elevations_h = [90.] + [26.57] * 5 + [52.62] * 5 + [10.81] * 5 + [69.16] * 5 + [
+        47.41] * 5 + [31.08] * 10 + [9.23] * 10
+    az1 = [0, 72, 144, 216, 288]
+    az2 = [36, 108, 180, 252, 324]
+    azimuths_h = [180.] + az1 + az2 * 2 + az1 * 2 + [
+        23.27, 48.73, 95.27, 120.73, 167.27, 192.73, 239.27, 264.73, 311.27, 336.73] + [
+        12.23, 59.77, 84.23, 131.77, 156.23, 203.77, 228.23, 275.77, 300.23, 347.77]
+    nb_sect = [1, 6, 16, 46][numpy.searchsorted([1, 6, 16, 46], min(46, sectors))]
+    return [*zip(elevations_h[:nb_sect], azimuths_h[:nb_sect])]
+
+def closest_point(point_grid, point_list):
+    dists = [numpy.sum((point_grid - p)**2, axis=2) for p in point_list]
+    return numpy.argmin(numpy.stack(dists, axis=2), axis=2)
+
+def sky_map(luminance_grid, luminance_map, directions):
+    _, _, az, z = luminance_grid
+
+    def _polar(az, z):
+        theta = numpy.radians(az)
+        return z * numpy.cos(theta), z * numpy.sin(theta)
+
+    grid_points = numpy.stack(_polar(az, z), axis=2)
+    target_points = numpy.array([_polar(a,90- el) for el,a in directions])
+    targets = closest_point(grid_points, target_points)
+    lums = numpy.bincount(targets.flatten(), weights=luminance_map.flatten())
+    smap = numpy.zeros_like(luminance_map)
+    for i, w in enumerate(lums):
+        smap[targets==i] = w
+    return lums, smap
 
 def show_sky(grid, sky, cmap='jet', shading='flat'):
     """Display sky luminance polar image