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Import OBJ Files

Technical specifications to import 3D geometries as OBJ

2.5D geometries (vertically extruded polygons) can be created in UrbanMetrix. More complex 3D geometries have to be imported as OBJ files.

Specifications

  • Only one OBJ file per object (custom obstruction, project sketch, etc.) can be uploaded.
  • The model must be one unique object.
  • The OBJ mash should be water thigh.
  • The coordinates in the file must be in x,y,z format. 
  • The Coordinates Reference System (CRS) is free. If it is a custom provide the translation in the upload panel, otherwise leave 0,0,0.
  • The unit of measure need to be in METERS.
  • Only faces with maximum 4 vertices are accepted.

How to prepare geometries in Rhinoceros 3D

1. Units

First of all make sure your model is in METERS: command Units.

If your model was in Millimeters for instances, then select the below option. To double check, command Distance and measure a known length.

 

2. Simple Water-tight mesh

To create a simple water-tight shell mesh, it is recommended to create such volume using the NURBS tools. 

 

Option A: Start from scratch with a model on a locked layer

  • Create Polylines, Extrude and Cap. 

 

Option B: Start from a Mesh model

  • Select the uppermost Slab surfaces 
  • Type toNURBS, OK
  • SelLast then MergeAllCoplanarsFaces

 

Option C: Start from a NURBS model on a locked layer

  • Select the uppermost Slab surfaces using the CTRL+Click on such surfaces. 
  • Type DupFaceBorder to get the outside curves. Type Join to be sure they are connected. 
  • Type PlanarSrf to get surfaces output.
  • Type ExtrudeSrf then move the mouse towards the bottom. 
  • Go into a side-view and drag a selection window from top left to bottom right while pressing CTRL+Shift around the bottom surfaces of the newly created extrusion. 
  • Then move the Gumball Blue square towards the center of the Gumball to make them all at the same level. 
  • Or with these bottom surfaces selected, type SetPt, only select the SetZ with WorldAxis. press OK, then type 0. Then move these bottom surfaces to a level you wish. 
  • These bottom surfaces should be located a few meters below the ground surface from UrbanMetrix, way more underground is no problem at all. 

 

For all the options, Use Join or BooleanUnion and MergeAllCoplanarsFaces commands to create a unified shell.

From this geometry, select it and convert it using the Mesh command. 

  1. Select the fewer polygons count as below.
  2. Check if the result is good enough. 

 

3. Locate and rotate the model into CH1903+ / LV95 Coord.

In your input model, locate the origin using the command Point, then type 0,0,0. 

Command SelLast to select this origin point. Command Lock to lock it.

Ideally this origin point should be on the cadastral boundary for easy translation towards the LV95 Coordinates. If not, select your model and the cadastral boundary and move them from a boundary corner to the origin. 

Rotation of the model should be North. If it is not the case, select all, command Rotate, type 0,0,0 a rotation center, then select an axis to be rotated towards the North.

Then to make sure the view is not rotated, in a Plan view, in the Properties panel, with no selection made, check that the camera rotation is set at 0.

https://map.geo.admin.ch/

On the above website, turn on the Geocatalo / Cadastre (...) / Availability of the PLR Cadastre. 

Locate your site and Right+Click the point your model origin should be placed.

Copy in your ClipBoard the CH1903+ / LV95 Coord.

Mark down the Elevation in METERS too.

In a text editor, rewrite the pasted coordinates

Format for Rhino

Input : 2'718'185.63, 1'096'456.02

Output : 2718185.63,1096456.02,277.7        (Note the formatting and no SPACING)

 

4. Move your Rhino model into the real world

In Rhino, select the Mesh you want to import in UrbanMetrix. 

Type Move, click on 0,0,0, paste the ClipBoard content with the LV95 coordinates. 

Type ZS to Zoom on your Selection and it should be in the new coordinates. 

Select the mesh and type Export. 

Select the folder you want to export it in. Select the format .OBJ. Unselect all the boxes and press Options. 

Make sure the export options are as below:

 

5. Import your model in a new UrbanMetrix Grid

Once a project has been created, click on Add Grid.

Follow the instruction on Add Grid and then tick the Building Sketch. Select the file to upload. Follow the same procedure if you have a Custom Obstruction you want to add to your site. Please note that the Building Sketch and the Custom Obstruction must be two separate OBJ models.

Click Finish and wait for the file to reach the server.

Create a simple Geodata with terrain and buildings to test it before further work.


Troubleshooting (WIP)


The model might appear wrongly rotated in UrbanMetrics. 

Option A: You can download the UM model without any layer in a Rhino 3DM format. Open it in Rhino and measure the angle of rotation between the two models of your building sketch. 

Option B: You can take a close up screenshot in a North-oriented 2D plan view in UrbanMetrix. Then Paste in Rhino at Z = 0m so that in a Rhino Plan View you see it underlaid. Then rotated accordingly.