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Can the geometry engine in 4.7 intersect a 3d line with a 3d polygon?

rhughes522

When using the geometry engine's intersect method and inputting a line geometry with z-values and a polygon with z-values, the result keeps returning a geometry identical to the input line.

Is this a supported operation by the api? While 3d is supported I cannot seem to find documentation on using the Geometry Engine with 3d features.

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RalucaNicola1

ok, here's a snippet, I hope it helps somehow: Edit fiddle - JSFiddle It is a very restrained case: polygons are planar, no inner rings and you always look at the intersection of a vertical line with the polygons. For the more complex case where your polygon is not planar you would have to triangulate the polygon and then check each triangle to see if it intersects with the line.

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KristianEkenes

Hi Richard. The Geometry Engine only supports 2D geometric operations. While geometries with z values can be used, they will be ignored for all evaluations.

rhughes522

Hi Kristian,

That is interesting. The API documentation does not really specify that so cut and dry. Also, the Identify Task is stated as not supported on 3d Scene Views. Turns out that because the geometry operations are not working on 3d data, we are using the Identify Task to query pixel values from rasters on a map service to get the differences in elevation between features. I understand that the extent of the Scene View could causes issues, but when Identifying by a point it works. What does "Not supported" mean in the context of the javascript api?

It would be nice to not have to generate rasters to calculate differences in elevation to determine if a feature intersects another. The Geometry Engine, based on the API seems like the correct solution. Is it that a Geometry Service is required instead so ArcServer can perform the intersect comparison?

Thanks,

Rich

RalucaNicola1

Hey Richard,

Can you tell us more about your use case? What are you trying to do? If you have vector features that have z values, why are you bringing in raster data?

Unfortunately we don't support 3D geometry operations for now, we write that in the geometryEngine documentation: geometryEngine | API Reference | ArcGIS API for JavaScript 4.7: "A client-side geometry engine for testing, measuring, and analyzing the spatial relationship between two or more 2D geometries."

rhughes522

Hi Raluca,

Thank you for pointing that out with the 2d geometries for the Geometry Engine. Seeing the Geodesic Buffers 3D kept pulling me towards the impossible.

What we are doing is showing penetrations in an airspace application. We want to identify what 3d surfaces are intersected by a vertical line representing an obstacle. We can see the intersection in the Scene, and we measuring them. The rasters in the map service are not being added to the app. They are being queried through an Identify Task (which is not supported in the Scene View) and the pixel values are used to calculate the differences in elevation between the surfaces at the specified point. Does that make sense? The data is then shown in a table in the app.

The need to create the rasters for calculating the difference in elevation is all they are for. The rasters are not visible in the Scene and are not used to create a layer, the url is used in an IdentifyTask.

We would like to be able to determine whether a vertical obstacle intersects a 3d polygon.

RalucaNicola1

rhughes522

Just after reading through the snippet it looks like that it what we are thinking of. Thanks for your help getting it going in the app. If I find enough time to put towards writing the equations in javascript, I'd love to be able to calculate the intersection myself, but my Calc and Trig are rusty.

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