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I have a 3D building model (Polygon ZM) that I would like to turn to DEM, following the accepted answer to Elevation data from 3D shapefile of buildings to raster DEM

According to the description, Polygon ZM should be first converted to TIN before I could convert it to raster.

For some reason, converting Polygon ZM to TIN leads to error so I did an additional step "Feature vertices to points" (1st image) before "Create TIN". This way I can produce a TIN (2nd image) but it is not quite similar to the original Polygon ZM. Any ideas how could I make the TIN more accurate? Result of "Feature vertices to points" Result of "Create TIN"

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    Maybe try running the densify tool on the polygons before conversion. – GBG Jul 10 '17 at 15:50
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    One issue you will have is converting a 3D building multipatch to tin because both TIN and DEM are 2.5D surfaces not 3D. TINS in ArcGIS are not like 3D mesh in CAD. You can improve the TIN by Editing the TIN and adding hardlines for the walls but you would need to create the hardlines and asign know the elevation of the hardlines. You could also try Editing the tin manually and snapping hardlines between the nodes. Things may get funky though with vertical walls and surfaces. Can you post a link to the shapefile? What's your ultimate goal? – Jakub Sisak GeoGraphics Jul 25 '17 at 17:54
  • @Jakub My ultimate goal is to produce a raster in which the gray scale value of each pixel represents the height of the building(s). For that purpose, I believe, I do not need vertical surfaces as the the pixels in the final outcome would represent the corresponding height of rooftops, not walls. Still, I need a method to convert all rooftops (withouth vertical surfaces as they would not be visible on the final raster outcome anyways) to TINs and then to rasterize them. (It works beautifully if I create TINs one by one for every single rooftop but I don´t know how to merge them.) – diners Aug 2 '17 at 11:34
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From how your TIN looks I incline to believe you have used only the points to create it. You can try the next variants to solve your issues:

  1. Create multiple polygons with Z values and use Interpolate shape. What I mean is that you create one polygon for roof side, one for interior and one for exterior side. Try to create a TIN for each polygon to check if everything is alright. If all good then you can merge the TINs.

  2. Instead of using Z aware polygons use Z aware lines. Mostly same procedure as above.

  3. Try using the Densify tool as @CBG suggested. Use a distance of 10 cm or less an see what results you get.

Creating a TIN in ArcGIS is easy and complicated at the same time. It took me a couple of hours to properly integrate an excavation in a current TIN, but the results are worth it. If you don't manage to solve on your own, share a sample of your data and I'll help as much as I can.

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