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Sun Shadow Volume

Summary

Creates closed volumes that model shadows cast by each feature using sunlight for a given date and time.

Usage

  • All input features should reside in the same locale, as relative sun position calculations are based on the position of the first feature in the first feature class.

  • Shadows modeling sunrise and sunset conditions can be made by providing only a date in the Start Date and Time and End Date and Time parameters, respectively. Shadow volumes will not be produced if the sun is not visible for a given date and time or if the relative position of the sun is at a vertical angle of 90 degrees from the input features.

  • Shadows are modeled as closed multipatches created by extruding the input features in the direction of sunlight. Light rays are considered to be parallel and travel in the direction calculated for the relative position of the sun. Each shadow volume starts and ends at a vertical plane that is perpendicular to the horizontal projection of the sun's rays.

  • The following fields will be attributed to the shadow volume features:

    • SOURCE—Name of the feature class casting the shadow volume.
    • SOURCE_ID—Unique ID of the feature casting the shadow volume.
    • DATE_TIME—Local date and time used to calculate sun position.
    • AZIMUTH—Angle in degrees between true north and the perpendicular projection of the sun's relative position down to the earth's horizon. Values range from 0 to 360.
    • VERT_ANGLE—Angle in degrees between the earth's horizon and the sun's relative position where the horizon defines 0 degrees and 90 degrees is directly above.
    Note:

    Typically, each shadow volume would appear to hug, or be cast tightly against, its originating feature. If a shadow could not be generated in this manner, it will be created from the boundary of the feature's outer extent. When at least one shadow is created this way, a field named HUGS_FEATR is included to indicate which shadows hug their corresponding features.

Syntax

SunShadowVolume_3d (in_features, start_date_and_time, out_feature_class, {adjusted_for_dst}, {time_zone}, {end_date_and_time}, {iteration_interval}, {iteration_unit})
ParameterExplanationData Type
in_features
[in_features,...]

The multipatch features that will be used to model shadows. Polygon and line features can also be used if they are added as an extruded 3D layer.

Feature Layer
start_date_and_time

The date and time that the trajectory of sunlight will be calculated for modeling the shadows.

Date
out_feature_class

The multipatch feature class that will store the resulting shadow volumes.

Feature Class
adjusted_for_dst
(Optional)

Specifies if time value is adjusted for Daylight Savings Time (DST).

  • ADJUSTED_FOR_DSTDST is observed.
  • NOT_ADJUSTED_FOR_DSTDST is not observed. This is the default.
Boolean
time_zone
(Optional)

The time zone in which the participating input is located. The default setting is the time zone to which the operating system is set.

String
end_date_and_time
(Optional)

The final date and time for calculating sun position. If only a date is provided, the final time is presumed to be sunset.

Date
iteration_interval
(Optional)

The value used to define the iteration of time from the start date.

Double
iteration_unit
(Optional)

The unit that defines the iteration value applied to the Start Date and Time.

  • DAYSIteration value will represent days. This is the default.
  • HOURSIteration value will represent one or more hours.
  • MINUTESIteration value will represent one or more minutes.
String

Code sample

SunShadowVolume example 1 (Python window)

The following sample demonstrates the use of this tool in the Python window.

arcpy.env.workspace = 'C:/data'
arcpy.SunShadowVolume_3d('sample.fgdb/buildings', 
                         start_date_and_time='12/25/2011 10:00 AM', 
                         out_feature_class='shadows_dec25.shp', 
                         adjusted_for_dst='ADJUSTED_FOR_DST', 
                         time_zone='Eastern_Standard_Time',
                         end_date_and_time='12/25/2011 3:00 PM', 
                         iteration_interval='HOURS', iteration_unit=1)
SunShadowVolume example 2 (stand-alone script)

The following sample demonstrates the use of this tool in a stand-alone Python script.

'''*********************************************************************
Name: Model Shadows For GeoVRML Models
Description: Creates a model of the shadows cast by GeoVRML models
             imported to a multipatch feature class for a range of dates
             and times. A range of times from the start time and end
             time can also be specified by setting the EnforceTimes
             Boolean to True. This sample is designed to be used in a
             script tool.
*********************************************************************'''
# Import system modules
import arcpy
from datetime import datetime, time, timedelta

#*************************  Script Variables  **************************
inFiles = arcpy.GetParameterAsText(0) # list of input features
spatialRef = arcpy.GetParameterAsText(1) # list of GeoVRML files
outFC = arcpy.GetParameterAsText(2) # multipatch from 3D files
inTimeZone = arcpy.GetParameterAsText(3) # time zone
startDate = arcpy.GetParameter(4) # starting date as datetime
endDate = arcpy.GetParameter(5) # ending date as datetime
dayInterval = arcpy.GetParameter(6) # day interval as long (0-365)
minInterval = arcpy.GetParameter(7) # minute interval as long (0-60)
enforceTime = arcpy.GetParameter(8) # minute interval as Boolean
outShadows = arcpy.GetParameterAsText(9) # output shadow models
outIntersection = arcpy.GetParameterAsText(10) # shadow & bldg intersection

# Function to find all possible date/time intervals for shadow modelling
def time_list():
    dt_result = [startDate]
    if dayInterval:
        if endDate: #Defines behavior when end date is supplied
            while startDate < endDate:
                startDate += timedelta(days=dayInterval)
                dt_result.append(startDate)
            dt_result.append(endDate)
        else: # Behavior when end date is not given
            daymonthyear = datetime.date(startDate)
            while startDate <= datetime(daymonthyear.year, 12, 31, 23, 59):
                startDate += timedelta(days=dayInterval)
                dt_result.append(startDate)
    return dt_result


importFC = arcpy.CreateUniqueName('geovrml_import', 'in_memory')

# Import GeoVRML files to in-memory feature
arcpy.ddd.Import3DFiles(inFiles, importFC, 'ONE_FILE_ONE_FEATURE',
                        spatialRef, 'Z_IS_UP', 'wrl')

# Ensure that building models are closed
arcpy.ddd.EncloseMultiPatch(importFC, outFC, 0.05)

# Discard in-memory feature
arcpy.management.Delete(importFC)
dt_result = time_list()
for dt in dt_result:
    if dt == dt_result[0]:
        shadows = outShadows
    else:
        shadows = arcpy.CreateUniqueName('shadow', 'in_memory')
    arcpy.ddd.SunShadowVolume(outFC, dt, shadows, 'ADJUST_FOR_DST',
                              inTimeZone, '', minInterval, 'MINUTES')
    if dt is not dt_result[0]:
        arcpy.management.Append(shadows, outShadows)
        arcpy.management.Delete(shadows)
arcpy.ddd.Intersect3D(outFC, outIntersection, outShadows, 'SOLID')

Licensing information

  • ArcGIS Desktop Basic: Requires 3D Analyst
  • ArcGIS Desktop Standard: Requires 3D Analyst
  • ArcGIS Desktop Advanced: Requires 3D Analyst

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