Summary
Generates a line or multipatch feature class containing the results from a skyline or silhouette analysis.
Illustration
Usage
The Skyline tool is often used in conjunction with the Skyline Barrier tool and sometimes with the Skyline Graph tool. Other applications of this tool are described in Analyzing threats to 3D flight paths and corridors.
The Skyline tool can be used to create feature silhouettes that can be extruded into shadow volumes with the Skyline Barrier tool. See further information in How Skyline works.
The following fields will be added to the output feature class that contains the skylines:
- OBSV_PT_ID—The FID of the observer point used to create this skyline.
- ORIGFTR_ID—FID of the feature, such as a building.
The following fields will be added to the output feature class that contains the silhouettes:
- OBSV_PT_ID—The FID of the observer point used to create this silhouette.
- ORIGFTR_ID—The FID of the original feature, such as a building, represented by this silhouette.
- DIR_VECT_X—The X component of the unit vector representing the direction of the light rays from the observer.
- DIR_VECT_Y—The Y component of the unit vector representing the direction of the light rays from the observer.
- DIR_VECT_Z—The Z component of the unit vector representing the direction of the light rays from the observer.
- FEAT_CTR_X—The X component of the center of the envelope of the original feature (for example, building).
- FEAT_CTR_Y—The Y component of the center of the envelope of the feature.
- FEAT_CTR_Z—The Z component of the center of the envelope of the feature.
- BHND_CTR_X—The X component of the center of the envelope of the feature, moved to behind the feature.
- BHND_CTR_Y—The Y component of the center of the envelope of the feature, moved to behind the feature.
- BHND_CTR_Z—The Z component of the center of the envelope of the feature, moved to behind the feature.
- USED_PARLL—Whether the silhouette was created using parallel light rays (1 for yes and 0 for no).
- MADE_VERT—Whether the silhouette was made vertical, rather than perpendicular to the light rays (1 for yes and 0 for no).
- MOVED_BHND—Whether the silhouette was moved to behind the feature, rather than staying at its center (1 for yes and 0 for no).
Syntax
Skyline_3d (in_observer_point_features, out_feature_class, {in_surface}, {virtual_surface_radius}, {virtual_surface_elevation}, {in_features}, {feature_lod}, {from_azimuth_value_or_field}, {to_azimuth_value_or_field}, {azimuth_increment_value_or_field}, {max_horizon_radius}, {segment_skyline}, {scale_to_percent}, {scale_according_to}, {scale_method}, {use_curvature}, {use_refraction}, {refraction_factor}, {pyramid_level_resolution}, {create_silhouettes})| Parameter | Explanation | Data Type |
in_observer_point_features | The 3D points representing observers. Each feature will have its own output. | Feature Layer |
out_feature_class | The 3D features that will either be lines that represent the skyline or multipatches that represent silhouettes. | Feature Class |
in_surface (Optional) | The topographic surface that will be used to define the horizon. If no surface is provided, then a virtual surface will be employed using the virtual_surface_radius and virtual_surface_elevation parameters. | LAS Dataset Layer; Mosaic Layer; Raster Layer; TIN Layer; Terrain Layer |
virtual_surface_radius (Optional) | The radius of the virtual surface that will be used to define the horizon when a topographic surface is not provided. The default is 1,000 meters. The following units are supported:
| Linear Unit |
virtual_surface_elevation (Optional) | The elevation of the virtual surface for defining the horizon in lieu of an actual surface. It is ignored if an actual surface is provided. The default is 0. The following units are supported:
| Linear Unit |
in_features [in_features,...] (Optional) | The features used in determining the skyline. If no features are specified, then the skyline will consist solely of the horizon line as defined by the topographic or virtual surface. | Feature Layer |
feature_lod (Optional) | The level of detail at which each feature should be examined in the skyline analysis.
| String |
from_azimuth_value_or_field (Optional) | Double; Field | |
to_azimuth_value_or_field (Optional) | The direction, in degrees, at which the skyline analysis should be completed. The analysis starts from the observer point and goes to the right, from the From Azimuth until the To Azimuth is reached. Must be no more than 360 greater than the From Azimuth. The default is 360. | Double; Field |
azimuth_increment_value_or_field (Optional) | The angular interval, in degrees, at which the horizon should be evaluated while conducting the skyline analysis between the From Azimuth and the To Azimuth. Must be no greater than the To Azimuth minus the From Azimuth. The default is 1. | Double; Field |
max_horizon_radius (Optional) | The maximum distance for which a horizon should be sought from the observer location. A value of zero indicates that there should be no limit imposed. The default is 0. The following units are supported:
| Linear Unit |
segment_skyline (Optional) | Determines whether the resulting skyline will have one feature for each observer point, or if each observer's skyline will be segmented by the unique elements that contribute to the skyline. If silhouettes are being generated, then this parameter will indicate whether divergent rays should be used; for sun shadows, this should generally be NO_SEGMENT_SKYLINE
| Boolean |
scale_to_percent (Optional) | Indicates to what percent of the original vertical angle (angle above the horizon, or angle of elevation) or elevation each skyline vertex should be placed. If either 0 or 100 is entered, then no scaling will occur. The default is 100. | Double |
scale_according_to (Optional) | The values according to which the scaling should be determined.
| String |
scale_method (Optional) | The vertex to be used to calculate against.
| String |
use_curvature (Optional) | Indicates whether the earth's curvature should be taken into consideration when generating the ridgeline from a functional surface.
| Boolean |
use_refraction (Optional) | Indicates whether atmospheric refraction will be applied when generating the ridgeline from a functional surface.
| Boolean |
refraction_factor (Optional) | The refraction coefficient to be used if atmospheric refraction is being considered. The default is 0.13. | Double |
pyramid_level_resolution (Optional) | The z-tolerance or window-size resolution of the terrain pyramid level that will be used by this tool. The default is 0, or full resolution. | Double |
create_silhouettes (Optional) | Specifies whether output features will represent skylines or silhouettes.
| Boolean |
Code sample
Skyline example 1 (Python window)
The following sample demonstrates the use of this tool in the Python window.
import arcpy
from arcpy import env
arcpy.CheckOutExtension("3D")
env.workspace = "C:/data"
arcpy.Skyline_3d("observers.shp", "skyline_output.shp", "sample.gdb/featuredataset/terrain")
Skyline example 2 (stand-alone script)
The following sample demonstrates the use of this tool in a stand-alone Python script.
'''****************************************************************************
Name: Skyline Example
Description: This script demonstrates how to use the
Skyline tool.
****************************************************************************'''
# Import system modules
import arcpy
import exceptions, sys, traceback
from arcpy import env
try:
# Obtain a license for the ArcGIS 3D Analyst extension
arcpy.CheckOutExtension('3D')
# Set environment settings
env.workspace = 'C:/data'
# Set Local Variables
inPts = "observers.shp"
# Make sure output has a unique name
outFC = arcpy.CreateUniqueName("skyline_output.shp")
inSurface = "sample.gdb/featuredataset/terrain"
obstructionFCs = "buildings.shp; billboards.shp"
surfRad = "1000 meters"
surfElev = "100 meters"
LOD = "FULL_DETAIL"
fromAzim = 0
toAzim = 360
incAzim = 1
maxHorizRad = 0
segSky = "SEGMENT_SKYLINE"
scale = 100
scaleAcc = "ELEVATION"
scaleMethod = "SKYLINE_MAXIMUM"
# Execute Skyline
arcpy.Skyline_3d(inPts, outFC, inSurface, surfRad, surfElev,
obstructionFCs, LOD, fromAzim, toAzim, incAzim,
maxHorizRad, segSky, scale, scaleAcc, scaleMethod)
except arcpy.ExecuteError:
print arcpy.GetMessages()
except:
# Get the traceback object
tb = sys.exc_info()[2]
tbinfo = traceback.format_tb(tb)[0]
# Concatenate error information into message string
pymsg = 'PYTHON ERRORS:\nTraceback info:\n{0}\nError Info:\n{1}'\
.format(tbinfo, str(sys.exc_info()[1]))
msgs = 'ArcPy ERRORS:\n {0}\n'.format(arcpy.GetMessages(2))
# Return python error messages for script tool or Python Window
arcpy.AddError(pymsg)
arcpy.AddError(msgs)
Environments
Licensing information
- ArcGIS Desktop Basic: Requires 3D Analyst
- ArcGIS Desktop Standard: Requires 3D Analyst
- ArcGIS Desktop Advanced: Requires 3D Analyst