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Aligned Hardscapes Create Site Modifier Conflicts

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I'm new to hardscape objects. It appears that two hardscape objects must be adjacent if they are to align to each other vertically. Since they act as site modifiers they also create many modifier conflicts. The warning flags say "Pads intersect" just like regular site modifier pads when they touch in plan view. Should I ignore these warnings? Is there a way to avoid them?


Thank you!


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Hi, Ed!

Did you resolve this? I was hoping @Tamsin Slatter or @Tony Kostreski or other with deeper knowlege would jump in here.  ???


I think that if the terrain updates and looks OK, then the warnings can be ignored . . .  but why put warnings for a non problem ??


So far, my experience is that pads with coincident edges, including the pads built into hardscape modifier objects, maybe even grade limits and other mods, produce the warnings, but not problems. Therefore OK to ignore. I think that only applies if same type of mod - ie Two pads can share an edge, but not a pad and a grade limits.  One example of this, I think, is the multiple pads created in a Road object . They seem to share edges with adjacent road panels. Or, maybe these have some micro offset at creation (can anyone verify?)


But if mods overlap, then the warnings appear, and other problems can happen such as slow/fail updates, funky surfaces, etc (so, edit to correct any overlaps).


Something else unclear to me is whether warnings can be ignored if two pad edges appear coincident in plan, but have different z, or if the these edges are not same slope.


Aligned slab with mod has a built in pad object.  Slab with retaining edge has also a built in 3d poly (the retaining edge, sort of a variable z Grade Limits), which is slightly offset, maybe about 1mm outboard. I believe two coincident Aligned Slab with Retaining Edge will have overlapping modifiers (unless these objects offset the pads inboard instead of the retaining edge offset outboard???).  This might work, but might get too complex and cause immediate or future crashes or freezes.  Might screw with the cut/fill calcs and slope analysis???   Better to use the plain modifier version and draw a new grade limits surrounding the colliding slabs.


Perhaps a strategy can help avoid warnings or problems:

Create hardscape objects but use the plain version, not the modifier version.  Apply all the slopes, then extract edges (3d tool set>Extract tool) from the bottom surfaces (makes NURBS), convert to 3d Polys. Assign those polys to the Site>DTM>Modifier class. Add a surrounding Grade Limits.  Update the terrain.  It will be cut to match the  z, slopes, and edges of the hardscapes.


Or make pads in advance (touching or slightly offset), surround with a grade limits object, then create the hardscapes to match.

Or intermittent - one hardscape is a modifier, adjacent one is not, next adjacent one is modifier type, etc.


Some things I try to keep in mind:

  • Vertices in a modifier connect to the nearest terrain mesh nodes or nearest vertices of other modifier objects.
  • Grade limits have the additional property that they automatically send to surface. So outboard, they interrupt the mesh (connect in place). Vertices of modifier objects inside the grade limits connect to each other, or to the vertices on the grade limits - whichever is shortest path.
  • Vectorworks terrain is supposedly incapable of vertical or overhung mesh segments (but I guess shared modifier edges are exception? as long as they do not overlap?)




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My understanding is that the built-in slab modifiers are designed for quick visuals only. They do not 'excavate' the site model in the way a standalone site modifier does so the volume of the hardscape is not factored into the cut calcs. Compare a hardscape with built-in modifier next to a hardscape with its own separate retaining edge pad in section + you will see the difference. The former is just a planar object whereas the latter is 3 dimensional.


But if you do use slab modifier hardscapes side by side yes I believe you are meant to offset them 1mm apart to avoid modifier conflicts. Or just ignore them 

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Thanks Benson & Tom. So far, I'm resolving this by ignoring the modifier conflict warnings. In my current project it appears that separating an aligned slab from the other objects (by even 1mm) prevents that slab from aligning with those objects. I'm using 3D polys, other hardscape objects and a roadway poly to control the shape of a twisted driveway. 


Tom - Thanks for mentioning the cut volume calcs. Yes, I see that the hardscapes do not offer an option for "Apply to existing" or "proposed". But I'll keep using the hardscapes unless the calcs become critical. I like to avoid static modifiers that need to be adjusted or recreated as the design changes. When I get to the point where I need cut & fill volumes then I'll try Benson's strategy of extracting the bottom surfaces to use as modifiers.


Benson - it seems like there's a lot to unpack in your "Some things I try to keep in mind". I don't understand the first two items but it seems like I might benefit if I did. Maybe they merit another separate discussion.


Thank you!


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Posted (edited)
15 hours ago, Tom W. said:

They do not 'excavate' the site model in the way a standalone site modifier does

Intended for informal visuals only? Never knew that!

Kind of alarming if not widely known. I don’t normally  need any cut/fill data so has not been an issue. But thanks for the notice. 

I will try to elaborate on my understanding of the ways mods affect a terrain mesh:

  • The algorithm for terrain mesh is that the 3d nodes (contour vertices, modifier vertices, stakes, loci)  “detect” the nearest nodes sideways, up, and down and connect with a segment. Depending on dispersion, any node might host many segment ends. 
  • The goal is create enough of these nearest neighbor connections to make the mesh with triangular faces throughout. No crisscrossing allowed.
  • Also,  no connections to same z beyond one nearest neighbor on either side. This sometimes fails, connecting to several nodes at same z, creating flat areas  on the terrain - there are some fixes.
  • A pad site modifier cancels the existing terrain nodes it surrounds and edges it intersects. Inboard, it connects its nodes to themselves (eg a rectangular pad will divide into two triangles with a new edge along one diagonal).  Outboard, the modifier follows the algorithm to connect to all nearest neighbor nodes eg the corners of a rectangular pad will connect many new edges to the nearby contour nodes.
  • A grade limits modifier, say a poly closely surrounding two pads, “remembers” the unmodified terrain (prior to the pads) and sends itself to that un modified surface. This is essentially a 3d poly, likely with many vertices. It cancels all edges it intersects, then makes new connections. Outboard it recreates any original terrain that was modified by pads. It connects its nodes to the nearby nodes of the contours. Inboard, it cancels effects of nodes of contours and other enclosed source data, but not of the enclosed site mods. The grade limits nodes connect to nearest pad corners. If the pads have separation, new edges are formed from pad to pad across that gap, rather than to the grade limits.
  • Question to vwx folks - Why is it called  “grade limits”??? With the s? Maybe Grade Limit? Or Grade Limiter? Or Limit? Or Anything less awkward . . .


Edited by Benson Shaw
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