Modelling underground drives

Follow the procedures below to model an underground tunnel network from a set of scans.

Tip:   Before modelling tunnels and other underground voids, filter out water reflections and other extraneous points for best results.

Tip:  Press P to set plan view manipulation mode, which is the most suitable view mode for this procedure.

1. Create tunnel surfaces

   1. Create a loop at the start of the drive with Underground > Loop Surface > Fit Loops (click Single Loop). See Loop Surface > Creating a single loop.

   2. Create multiple loops to the end of the section of the drive with Underground > Loop Surface > Fit Loops (click Multi Loop). See Loop Surface > Creating multiple loops.

   3. Check loops and fix any errors, as required.

   4. Create loop surfaces with Underground > Loop Surface > Loop Surface. See Loop Surface.

   5. Repeat steps 1-4 with other drive sections that need to be modelled.

2. Join intersections

   1. Remove facets across tunnel intersections by selecting them with the (Select facets) type, then pressing Delete.

   2. Select all surfaces to be joined and run the Loop Surface tool with Loop ordering set to Iterative.

3. Merge into a single surface

   1. Select facets encompassing the areas where all the surfaces meet.

   2. On the Edit ribbon tab, in the Fix group, click Join and Close. See Fix > Join and close.

      The result is a single surface object.

4. Close ends

   Closing ends completes the underground model as a closed solid. How you close tunnel ends depends on whether there is scan data available for those ends.

   With data

   Where scan data exists, you can create tunnel ends that represent the actual surface shape.

   Note:  Always do this before closing ends without data.

   1. Create loops at tunnel ends with Create > Topography > Surface Boundaries. Clear the Merge boundaries into a single object checkbox.

   2. Filter the scans used to create the surfaces with Position and Filter > Filter > Minimum Separation. Set Minimum distance to 0.1 m (or equivalent in preferred units) and clear Apply filter to selection as a whole.

   3. Crop the scan with data at the tunnel end to show only the data outside the end of the surface.

   4. Select the boundary loop at the end of the surface.

   5. Create a surface from the tunnel end points with Create > Surface > Spherical Surface (see Surface > Spherical Surface):

      1. Set Spherical type to Surface.

      2. Right-click a Spherical origin point field and select Selection centre.

      3. Click on a Look point field, and pick a point at the centre of the wall at the end of the drive.

      4. Clear Trim long triangles.

      5. Select Split triangulation along edge constraints.

      6. Select both the boundary edge and its associated scan in the project explorer and click OK.

   6. Identify and delete any surfaces from the spherical container that are not required.

   7. Select the facets from both surfaces where they meet, then merge the surfaces with Edit > Fix > Join and Close.

   Without data

   Where there is no scan data at the tunnel ends, close the ends with a flat surface.

   1. Select the surface.

   2. On the Edit ribbon tab, in the Fix group, click Join and Close.