CR: Hypermodeling: Detail Views <> Compound Cells LOD switching

LOD is still a hot topic: I was wondering if the improvements to 'view dependent' Compound Cells can be steered by what Dynamic/Building Views are doing.

At the moment, Bentley's Hypermodeling (DV 3.0) can 'back-ref' 2d drawing information into the 3d model. This is great for viewing detailed 2d section information in its 3d context. Super kudos to Ray, John, Sunand and Rob.

This functionality is pretty useful, as it sidesteps the need to build in lots of detail/LOD into the 3d model just to get usable extractions, by 'diverting' the detail into 2d drawing 'planes' stored outside of the 3d model.

The 'problem' is that the info is confined to the cut plane. BIM is about providing or 'infusing' the appropriate information not matter where you cut the model. In terms of DV's, this means if the user uses the green handles to slide the cut plane, the relevant annotation, embellishments etc would still dynamically update.

Looking at the new Grid System tools being introduced in BBD, I was wondering if the new more 'view dependent' Compound Cells couldn't help. The View Attributes BV panel has a 'Show Grids' toggle that controls the visibility of the GS cells that re-symbolise themselves differently, depending on the view.

Maybe we should also have a LOD toggle as well. This could be geared to the AIA's LOD 100-500 scale if required... or just fine,medium and coarse... etc.

Say we have a cell for a door. C-Cells already allow the user to define a 'Drawing Symbol' proxy that replaces the normal 3d section or forward graphics. When generating the C-Cell, It should be relatively easy to just to define a slightly different level mask for the different LOD's. So, when the display system starts cutting the C-Cells, it would first load/cache the corresponding cells, with the appropriate levels containing the additional elements, into the display pipeline. The additional elements may be 3d elements, 2d elements including annotation/dimensions.

A LOD 100 door would correspond to what is delivered for 3d use with BBD today. The display system would load and cut simple extruded meshes. If a higher LOD was selected, then additional elements like hinges, ironmongery etc, defined on separate levels, could be loaded and cut. Additional 2d embellishment and annotation could be called up in the same way.

Similarly, a LOD 100 beam would just have its 'solid' extruded element called up by the display system. A higher LOD beam would have the levels for the rebar turned on or generated on the fly based on Drawing Rules xml settings, like the Grid System cell does? So, no matter how the beam is cut, there is a way to bump the LOD up/down dynamically.

A LOD 100 drywall would be modeled as a single TF-style linear form. A higher LOD drywall would have all the plasterboard layers and studs. Again, managed by making the cell 'view dependent' ie. context sensitive by either simply turning levels on/off or triggering some regeneration based on stored parameters. What happens the individual drywall run gets modified? If it is done parametrically, then the higher LOD wall can regenerated by 're-playing' or 're-hydrating' the stored parameters. If the mods were done using 'direct-modeling' tools, then the cell would be defined as a separate unique C-Cell, and the LOD controlled by switching levels on/off ie visibility.

So, no matter where the model is cut, the apporiate LOD-specific model/cell gets 'back-ref'd into place for the display system to process. Why do it via C-Cells and not just referencing more levels via models? I guess doing it at cell level is more granular. You typically need the additional LOD at the cut plane. I think it would be quicker to just call the higher LOD elements 'caught' by the cut plane, than to load everything just to get the LOD required... at the cut plane.

What if you need high LOD in the forward view as well? I can see this being useful for all those curtain wall/facade detail drawings. I would keep things speedy by limiting the Forward View, sensitivity depth. Separate LOD setting toggles for Forward, Cut and Back would be good.

What about those embellishments and additional lines, shapes, hatches etc that we added to those details? If the assembly can be defined as a C-Cell, then you could just click on the assembly and 'back-ref' the approriate 'detail sheet' that would be stored in the C-Cell. The back-up would be to place multiple Callouts that woud need to be re-pathed back to the appropriate detail sheet.