Combining Surfaces Issue

[hoom_afshar]

Hello,

I want to make a 3d model of a train station (it should be like the uploaded image). The problem is with the island platform. for this, I made a surface of the terrain, a surface for the island platform top, and 2 other surfaces for 2 sides of it (using by grading) . But when I wanted to combine all the surfaces, it recreated the triangulations, so the shape of the island platform changed (Image 2). 
I did the same procedure for the left platform and it made it correctly. I tried with the breaklines to fix this but nothing changed. 
Thanks for your help.

[nkiakas]

Hi @hoom_afshar

From what i see i could suggest you to do any of the below

• Looks like the you are going well will your design, till you insert in your design the platform as result (surface) of grading tools. Ok, if its possible and not complicated, try to make the full rail station, including platform, in one only grading.
• Or, create feature line(s) with the elevations from your surfaces before merge them. After merging, add the feature line(s) as break lines in the final surface, but be careful to add them as "wall break line", because i think this is your problem, the verticality of the median platform.

Let me know if the above helped

[matt_anderson_pe]

@hoom_afshar 

During the surface paste - the order or precedence of the ground matching of the island's grading got lost.

If you know the footprint of the island, use that to create a gap or a "hide" boundary in the base before pasting. 

[satkinsZGYU7]

I think I understand what you're trying to do. I use this same tactic to add buildings to my surfaces.

I assume you have a boundary for your rail platform. Offset that boundary outwards by 0.1', or some small number. All you need is a polyline for the offset; You don't need any elevations on it. Add that polyline offset to your combined surface as a non-destructive breakline:

Order this operation so that it occurs before the paste of your proposed surface, but after the paste of your existing. The operation order in your combined surface will look like this:

This will solve your problem.

@matt_anderson_pe mentioned hide boundaries, but they will leave an undesirable hole in the transition area from surface to surface: 

I'm assuming you want your surface to be continuous, with a sort of wall around the edge of your proposed area:

(Yes, I'm aware that after the final surface paste, you could add that same hide boundary as a show boundary, but at that point, why not just use a non-destructive breakline? It does exactly what you want with less steps.)

[chriscowgill7373]

As soon as you add a boundary to a surface that has surfaces pasted into it, it treats it as though all the pasted surfaces no longer have a boundary.   I cant tell from your description if that is something that is occurring.   Are you able to share the drawing information?