# Getting z-Value from xy-Values within IPolygon using ArcObjects?

How can I get the z-Value of given xy-Values within an IPolygon?

I have an IPolygon, which is zAware. For given xy-Values I want to get the z-Value of the Polygon-Shape. What I want to do is something like intersecting the Polygon with an vertical line and getting the Intersecting Point.

Has anyone an idea how to do something like this?

-

There is no Inbuilt way to do this. A z-aware polygon, is fundamentally not 3 D in itself. What is Z Aware are the vertices. So for a point inside the polygon (i.e. inside in the sense of X-Y domain) no Z value is defined.

(If you having problems, visualizing this, imagine a z aware polygon that does not lie in one plane. Some points are on that plane, some above and some below. For this polygon, only the vertices have a defined z value, and not any points in the interior.)

So you can proceed in several ways:

1. If you are assuming that the vertices are sort of spot heights, then the inside of the polygon is the surface in between the points is the 3 dimensional surface which is defined by these spots heights.
2. Another way would be to convert this geometry into a Multipatch, where the surfaces are defined as triangles. There you can find the z value at any point.
-
Thank you for your Answer. Well, I already suspected that it won't go easy :) Now I converted my polygon to a multipatch and got a new Problem. How to get the z-Value within the multipatch? You wrote, that it is possible to find the z-Value at any point within the triangle. But how? – user3668 Jul 15 '11 at 9:43
Are you on ArcGIS 10? You can use help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/… – Devdatta Tengshe Jul 15 '11 at 14:35
Yes, I'm on AG10. – aja Jul 18 '11 at 4:57
But I think, this link won't help me. I don't have a whole multipatch featureClass, only several geometries. Is there no other way then using Geoprocessing? GP seems to be yery slowly in batch jobs, so I would prefer not to use it. Thank you for your help ... – aja Jul 18 '11 at 5:04