Casting shadow on polylines

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02-12-2016 01:23 PM
JúlioLuta
New Contributor III

Hi,

Can I - using shadow volumes - interpolate its values in polylines? (Like we interpolate z values from topography)

I have 3d polylines and I'll model the buildings, can I using these inputs store somehow the shadow/sun in every polyline?

I also have the raster topography layer and can create a terrain surface if this would allow me to have a sort of raster sun shadow layer that could be used to interpolate sun shadow values on polylines.

I'm still a bit confused about the Sun Shadow Volume tool and I'm not that experienced with ArcGIS so I'm just speculating.

Cheers

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DanPatterson_Retired
MVP Esteemed Contributor

they are stored as closed multipatches

Sun Shadow Volume—Help | ArcGIS for Desktop

and conversions are listed here

Multipatch to Raster—Help | ArcGIS for Desktop

Multipatch To Collada—Help | ArcGIS for Desktop 

not sure what you are looking for though

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JúlioLuta
New Contributor III

Thanks for the reply.

In the Sun Shadow Volume:

- To confirm if I understood correctly, I need to use the 3d buildings and the terrain right?

- The terrain can be in a raster layer or should I model it in a different feature?

To simplify and dividing it into steps, what I need to do:

1a- Create sun polygons and shade polygons from the sun shadow raster/multipatch.

or

1b- Intercept polylines with the shade part of the raster/multipatch and do a second intercept with the sun part.

and

2- Store in the polylines I already have in which polygon(or polyline group) they are the most. If they are >50% inside the sun polygon I'd store 1, otherwise 0.

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DanPatterson_Retired
MVP Esteemed Contributor

You will have to report on your suggested workflow since I dont have the data to test myself to confirm... report back

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JúlioLuta
New Contributor III

I just read about the Intersect 3D Line With Multipatch so in the next days I'll try to test the workflow.

Creating buildings in AutoCAD -> Sketch Up -> ArcGIS -> Create Sun Shadow Volume -> Intercept with the polylines I have.

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JúlioLuta
New Contributor III

This methodology didn't have the results I wanted but with additional steps it might work.

With the Intersect 3D Line With Multipatch I can get the lines that touch the Shadow Volume surface (it doesn't output the ones that are inside the Shadow Volume but don't touch the surface.

I can cut those lines at the output intersection points.

Then I can use Inside 3D to these lines and I'll get the lines inside the Shadow Volume and touch the surface (already cut) and Inside 3D to the original lines to get the ones inside that don't touch the surface.

Unfortunately the Create Sun Shadow Volume can't have as secondary input the terrain. I tried to cut the Sun Shadow Volume at the terrain by intersecting it with a extrusion between the terrain and a plane above the buildings to then use multipatch footprint... but I always get errors with the Intersection 3D, always. I even tried with smaller volumes. I could later use the resulting polygons instead of all the lines I'm creating with the above process.

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