A dump truck is backing up...

[etornberg]

A hypothetical question for you Reviteers: Let's say you have a nice foundation with spread footings, stemwalls, and some wonderful building above. A large truck is going to come in and dump gravel that will fill in the bottom of excavation, in between all the footings (including those isolated column footings that keep changing size), then cover the tops of footings and go a foot or so up the stemwalls/pedestals etc. A slab will go above the fill. The bottom of slab has a different slope than the bottom of your excavation (pad anyone?), because you always scrape the bottom of excavation level, but the slab is sloped, so the fill has varying thickness.

How would you model that in the wonderful world of BIM? Would you bother? Would you just use filled regions on the sections? Hoping to learn something here...

[xSmiffyx]

I've never modelled the back fill to footings usually I build the footing with wall on top etc and add the fill as a hatch on the 2D views/sections you create.

I think it would be to complex to be model the actual fill i could be wrong.

[damon.sidel]

I agree with xSmiffyx mostly. I doesn't seem like something that necessarily needs to be modeled. That said, here's how I'd do it if it was necessary:
1. Draw the pad quite a bit below the fill. Using view templates, make sure it is hidden in all sections.
2. Create an in-place family for the fill. It would consist of two extrusions, the first would be earth from the level of the pad to the underside of the fill, the second would be the fill. If the fill slopes in only one direction, then I'd create the extrusions in elevation/section. If it slopes in two directions, it would be a little trickier, but possible.
3. Draw a floor on top of the fill for the bottom-most slab.

[etornberg]

I tend to only use the building pad tool as a pencil-thin layer at bottom of footing - it seems too limited for flexible use.
What I like about Revit is that it is good enough now to produce nearly fully modeled building sections (at say 1/4" scale, not detailed) - the soil interface is one last hang-up. Toposurfaces are fine until you want to start showing buried materials with vertically and sloped delineated surfaces.

We need Autodesk to put a little GIM into that BIM! (Geotechnical Information Modeling).

On reflection, it is whenever we depart from orthogonal extrusions that our work (and the work of the developers) gets complicated. Until we discover how to sculpt a 3-D holographic feature with computers we are stuck jumping from one 2-D plane to another. I wonder how car designers do their thing these days - do they still sculpt in clay?

[greg.mcdowell]

I would only suggest modeling them (perhaps as a line-based family) if you needed to calculate the volume of material.

[damon.sidel]

We need Autodesk to put a little GIM into that BIM! (Geotechnical Information Modeling).

I heartily agree the topo tools need more love! If you haven't already, you should vote for your favorite wishlist items.

I wonder how car designers do their thing these days - do they still sculpt in clay?

3ds Max, Maya, Rhino3D, ZBrush, just to name a few, are much more flexible in terms of geometry creation, (not to mention the Revit conceptual massing tools). I don't think we need a 3d holographic feature to do some wonderful designs, we just need Revit to catch up to the rest of the 3d modeling software in terms of creating complex geometry. The technology exists and has for quite some time now.