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Editing site model contours

Tom W.

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I recently attempted to edit the proposed contours on a site model + ended up making a complete mess of the terrain in the area in question. After exiting the edit mode, all looked fine in Top/Plan but when I changed to a 3D view I could see that in between my contours the terrain had lots of dips/holes/sharp edges + general irregularities. When I reduce the interval between the contours in the settings to display more lines, I could see that the intermediate contours were very twisted + messy + were the cause of the surface defects I was seeing in 3D. I then spent a fruitless half an hour trying to tidy up these contours in the edit mode but it didn't really have any effect. In fact, the more I tried to tidy things up the worse it looked.


Is this expected behaviour or had I done something wrong to cause it or is it something wrong with the particular file or site model? I have seen tutorials where contours are edited + distinctly remember somewhere being advised to increase the contour interval before entering the edit mode in order to reduce the amount of contours you have to manipulate, the idea being that the hidden contours in between the ones being edited will follow suit. But this is not at all what happened to me in this case.


Just be interested if anyone else more experienced than me has had the same thing. I will try it in another site model + see if the same thing happens... Wonder whether I've got a dodgy site model...

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We've been building a mine surface model about 1 kilometre across and been finding ways to work (we're both on VW 2018 and finding a few things don't transfer between platforms). Our aim is a simultaneous earthworks cut minimisation, and a visual profile for planning consent.


We did spend a lot of time cleaning / simplifying our data before bringing into VW to get the size down (we're at 400Mb and about to have a major clean - our project area in VW is about 250 square km, although that's mostly cadastral with a site model here and there).


We set our Minor contour interval at 5m, and Major at 0, which seemed to help. We've had some artifacts with contours that are deeply concave in plan view. We have got to the point where we trust the calculated volumes, and very happy each time we reduce them by 50000 cubes or so.


In edit mode we've opted for the tedious method of converting 3D poly's to 2D (as there's more edit options), doing the edits and converting back, entirely unautomated, but it works - only worthwhile as this is a high-value job. I've always avoided VW 3D but with 2018 it's a lot easier and it's an essential with this particular contract.

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  • 3 weeks later...

I have experienced similar problems, where editing proposed contours is totally unreliable, and just causes more problems. I have not used VW yet on a huge number of projects, and none of which required a cut/fill analysis so I just edited source contours or existing first sometimes to get clean results. Or, just used various site modifiers rather than try to edit the contours.

Not sure what the issue is...

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  • 2 weeks later...

I've recently worked with a couple of extremely steep sites and attempted for about 3 days to battle the same weird 3d behaviour: sudden jumps in contours, giant cliffs, holes, sudden peaks, unexpected contour changes in response to adjustments elsewhere and persistent errors while applying numerous modifiers at once...


I stopped and researched the issues... and I found a Design Summit talk by an engineer (DTM team leader?) explaining DTM workings in a technical, but understandable language. Not a riveting presentation, but an enlightening one. This led me to develop a workflow that actually produced the results for me (mostly...), at least for the visual aspects.


Instead of modifying the contours in DTM, I modified them in 2D (converted from 3D source data), deleting the unneeded ones, making new ones, etc... ensuring that they were not exactly one over another. Bringing this back into 3d and then into DTM mostly worked. A rather tedious process, but still better than 3 fruitless days of frustration...

Placing 3d loci at known locations (buildings grade points, other geodetic elevations) and using them as source data works great for smaller projects, but the modification issues remain - one can't simply cut a hole for a building.


I really wish DTM worked better. It would be far more useful if it allowed 3D points to be placed directly one over another, if one could directly query any point to get full xyz coordinates (this goes for every object we create, OI palette could give project and layer z in addition to xy and area without any extra clicks) and, most importantly, if it could interact with other objects. Instead of attempting to create a pad (useful for the land configuration, but a multi-step process) one could simply place the foundations of the building at the right geodetic elevation if it could simply cut the terrain model to accommodate it. At the moment numerous conversions and exports are needed to be able to at least subtract solids, but then there is no easy way back to DTM...


I realize this transition won't be trivial given the current primacy of 2d data, but I'm just dreaming of a real, full 3D... (or maybe I'm in my covid brain fog...)   

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