Is there any way to obtain the shadow range (Polygon Feature layer) of a Multipatch object on the ground?

YinglongDeng

Hello everyone, I'm currently using the ArcGIS Pro SDK for related 3D secondary development. I'm using C# and I'm encountering a problem now. I want to know if there is any way to obtain the shadow on the ground of the 3D object. I want to convert this shadow on the ground into a surface file (SHP or Polygon). I wonder if there is a way to achieve it. I only want the range of the shadow part on the ground and convert it into a surface feature file(Polygon Feature layer).Thank you all!

 

YinglongDeng

Thank you both in the comment section for the inspiration you gave me. Based on some of their hints, I have already solved this problem. I'll share my process of solving it. If there are any mistakes, I hope everyone can point them out to me.

First, use C# code to call geoprocessing tools, and use the Sun Shadow Volume (3D Analyst) tool to obtain a shadow volume. Then, when opening the property table of this shadow volume, it can be found that there will be AZIMUTH and VERT_ANGLE. They respectively represent the solar azimuth Angle and the solar altitude Angle at different times. We draw a ray with these two angles and points respectively. The starting point of the ray is the point above the ground in this MultiPatch. Assuming this ray is 1000 meters, the ending point is the end point of this ray. In this way, we can draw all the point rays above the ground in this MultiPatch. (As shown in the picture below.)

Then, by calling geoprocessing tools With C# code and using the Intersect 3D Line With Surface (3D Analyst) tool, the intersection points of these rays and the ground can be obtained. By using these points that intersect with the ground and the points where MultiPatch intersects with the ground, we can create a Polygon, which is the shadow range produced by our MultiPatch at the specified time. Finally, you can export this Polygon as an SHP file.

I sincerely hope that the official team of Esri Company will include this API in future versions. I think it is very useful in certain scenarios!

/*
A method for generating rays based on one point, two angles, and a specified length.
startX---Ray starting point
startY---Ray endpoint
azimuth---the solar azimuth Angle
angle---the solar altitude Angle
length---Ray length
**line--->>>>Ray**
*/
Coordinate3D coordinate3D = new(startX, startY, h);
double azimuth = 123.576939;
double angle = 12.466601;
double length = 1000.0;
MapPoint startPoint = MapPointBuilderEx.CreateMapPoint(coordinate3D, SpatialReferences.WebMercator);
double azRad = azimuth * Math.PI / 180.0;
double anRad = angle * Math.PI / 180.0;
double dx = -Math.Cos(anRad) * Math.Sin(azRad);
double dy = -Math.Cos(anRad) * Math.Cos(azRad);
double dz = -Math.Sin(anRad);
MapPoint endPoint = MapPointBuilderEx.CreateMapPoint(startPoint.X + length * dx, startPoint.Y + length * dy, startPoint.Z + length * dz, startPoint.SpatialReference);
ArcGIS.Core.Geometry.Polyline line = PolylineBuilderEx.CreatePolyline([startPoint, endPoint]);