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# How do I give a non-flat 3D polygon depth?

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I thought I could use shell solid, but it's not allowing me to select the face if there is any 'twist' to the 3d poly.

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Couple ideas

1.  Slice an extrude with surface based on your 3d poly.

2.  Make a terrain from your 3d poly.

Use the 2d poly as source for a landscape area with thickness.

Landscape Area>Convert to Group = Mesh.

Or are you trying to do something else?

Note that a 3d poly is a perimeter, not a surface. It can have several trimesh schemes from same vertices employing straight connectors and flat facets.  Add concepts of quadmesh and varimesh and curved connectors and curved faces to reveal infinitely many interpretations of surface from a 3d poly. VWX needs guidance when asked to make a surface and generate a volume from a 3d poly.

-B

Edited by Benson Shaw
trimesh?
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That is just the shape I'm trying to get - these are great ideas!

I thought of throwing this question into the big is-vectorworks-able-to-do-professional-grading post, as I'm trying to do some monolithic pavers that slope down a grade and then turn half way.

I had nice 'aligned hardscapes' and 'edit surface modifiers' when the slabs were just solids:

This worked well but the design changes so that there are 'troughs' across the slab every 4' to give the effect of separate pavers.

'Subtract 3D object from slab' seemed the way to go. But then you don't have all the grading controls that hardscapes have.

So I thought I would model the negatives to subtract.

It got over my head at this transition piece... sloping in multiple directions and the 3D poly would not extrude.

I'll try a couple of you ideas and see if I can get it to work.

I can always just hand draw the sections....

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It would be nice to have a combined slab/hardscape tool - one with better control of course!

...and now I've been reading that Landscape Areas are the recommended option to create hardscapes!

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@Benson Shaw Your work flow seemed to work, thankyou.

NOTES:

• I couldn't find covert to surface in my modify menu - but ctrl-alt-K worked fine.
• When I tried to 'section solids' the second time, it just cut the bottom off again (I didn't understand your 'reverse section' note)... but i just copied the solid section and moved the copy up and subtracted solid.

• In top/plan all the fold lines where visible: I tried auto-hybid and 2d/3d symbol.

Auto-hybid always had a clipped corner no matter where I set the cut plane.

But 2D/3D symbol works well for me.

Now I'm going to bring this object into my original drawing and try to 'subtract 3D object from slab' and see what I get - Again thank you!

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Maybe a combo with slabs and direct modeling could work?

Set up the grading through hardscape slabs or aligned slabs, or @Laura Stone idea of Landscape Areas, but no notches.

When design is final, extract the long bottom edges.

Or skip the slabs and just draw NURBS curves (corner point rather than wavy) through known edge elevations.

Make a loft between them and shell.  Then make the notches via one or many solid subtractions so 3d and all the sections are consistent.  I think there is a way to show grades on solids geometry, but I have not explored.

-B

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9 minutes ago, hollister design Studio said:

I couldn't find covert to surface in my modify menu

For future reference 'Create Surface from Curves' lives in the Model>3D Power Pack menu

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Sorry, I called it Convert to Surface. My own shorthand.  I mean the Create Surface from Curves command in the Model menu>3d Power Pack.

Re Reverse:

When you make a Solid Section, vwx chooses which side of the cut to display, I think based on direction of the cutting surface's normal.  OIP has a Reverse button to display the other side instead.

HTH

Edited by Benson Shaw
create/convert
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Doh!  @TomW 'splained it first.  Good one!

-B

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I always stayed away from NURBS and subdivision modeling as they were so imprecise when modeling in MAYA.

Plus MAYA's polygon editing is close to perfect and I never needed them!

...but it looks like I'm going to have to take the NURBS dive!

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My approach would have been less sophisticated than those described by @Benson Shaw ... I would convert the 3d polygon to mesh and then to generic solid, then I'd duplicate it, move the duplicate up or down by the desired Z value, manually draw 3d polygons to make the "sides" connecting the two meshes, and then do an add solids of everything to get the end result.

Reading this:

16 hours ago, Benson Shaw said:

Note that a 3d poly is a perimeter, not a surface. It can have several trimesh schemes from same vertices employing straight connectors and flat facets.  Add concepts of quadmesh and varimesh and curved connectors and curved faces to reveal infinitely many interpretations of surface from a 3d poly. VWX needs guidance when asked to make a surface and generate a volume from a 3d poly.

has been very helpful for my understanding of what a 3d polygon actually is.

VW seems to understand that if I draw a 3d polygon all on the same plane, it's a flat "surface", because it will let me extrude it.

Also useful to have it pointed out that there are several different possible trimeshes that can be made from a 3d poly. As VW will convert a 3d poly into a mesh... it must somehow make its own decision about which one to choose. Is there a rule for how this happens?

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3 hours ago, hollister design Studio said:

I always stayed away from NURBS and subdivision modeling as they were so imprecise when modeling in MAYA.

Plus MAYA's polygon editing is close to perfect and I never needed them!

...but it looks like I'm going to have to take the NURBS dive!

I find using NURBS useful in many cases but also often hard to control, partly thanks to a lack of documentation about how they actually work in VW, which I have complained about several times.

I also find that they are useful for generating one-off objects but as soon as you want to fit anything to them, they become very inaccurate, so when I've got curves where I need things to fit together exactly, I often end up resorting to segmentedlines instead of true curves. There's an additional problem with the way VW renders gradual curves, which has been the subject of a few lengthy threads.

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5 hours ago, line-weight said:

Is there a rule for how this happens?

Probably a rather involved sequence??  I think if the perimeter and internal connectors are provided the mesh converts that way.  Need to test!

-B

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A note about thickness

in my examples above and @line-weight’s process, the resulting solid has a constant z thickness, which is not same as concentric thickness (just now invented that term). A solid volume between two like surfaces with only z offset exhibits constant z. A shell, formed by offsetting everywhere along the normals to the source object exhibits concentric thickness.  Volumes would be very different.

-B

Edited by Benson Shaw
Tablet typing
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Shell doesn't work on a 3d polygon - is that right? Has to be converted to a generic solid first?

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It will if it's a planar 3D Polygon but not if it's 3D/twisted. Then you need to convert to mesh then to generic solid as you posted above. Or you can convert to NURBS Curve then to Surface. But you get different results with the way the object triangulates between the two methods which is weird. Plus then because you are shelling the different individual facets you end up with a not especially satisfactory solid at the end. Or at least that has been my limited experience. I used the Site Model>Landscape Area>Generic Solid technique @Benson Shaw talked about above when I needed to give a complex surface thickness. Shell Solid was no use at all

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That is a really useful technique thank you @Katarina Ollikainen! So use 'Extrude Mode' to extrude the initial subdivision object then 'Close Mode' to put a lid on the resultant shell. Then when you convert to Generic Solid the hollow interior gets filled in. Cool

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Yeah, this is why Katarina gets paid the bug bucks 🙂

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Correction...BIG bucks. 🙂

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