Revit to Max model Stat Analysis

[Crazy Homeless Guy]

Here are some interesting stats…

 

I recently spent time revisiting the workflow between Max2011 and Revit2011. These are the results of different Links and Imports. Quiet a variation in the number of vertices, and the spead of the model once it was inside of Max. This was the first round of testing, I have not done the second round yet.

 

The numbers are all from the same model.

 

I haven’t fully wrapped my head around this info to figure out what my next best step is, but I thought I would share anyway, since this type of information is useful for many on this forum.

[Justin Hunt]

interesting, have you tried FBX import? I have found a difference between import and FBX Link. mainly in how curved walls are meshed in Max. FBX Link couldn't mesh it properly by forming faces across the curve making a mess of a mesh. Whereas FBX import meshed it properly.

 

The other thing that is confusing me is the units. The Revit model is in mm and Max is in meters and cm (system and display). The model is correctly sized but the material scales are way off. It looks like the objects system units are sill mm. A "Reset XForm" and collaps to poly fixes the problem.

 

jhv

[Crazy Homeless Guy]

I haven't tried Linking vs Importing on the FBX.

 

I think this screenshot was from 2010, and not 2011, but it shows a problem I have had with cylinders that have a bend in the past. They are rubbish.

[Justin Hunt]

also the way FBX tessalates ramps in 2010 made them almost unusable. Things are a bit better in 2011 but still not there yet.

 

jhv

[pfbreton]

Let me try to clarify a few things ...

 

..about curved objects:

 

 

When exporting Revit to DWG, tesselation is made by revit unless you export to solids. In that case, when importing the dwg in max, those solids objects are tesselated by the Max dwg import.

 

When exporting to FBX from Revit, curved objects are tesselated to meshes by Revit. In fact, a FBX export in Revit is goind through the same code path (or almost) as a Render in revit.

 

In an ideal world, Max would retain solid entities and manage the tesselation to meshes on its end, but it is currently not something possible with the existing toolsets - but we are aware of the problem.

 

To work around it, there might be a few strategies you could adopt. For example, you could set up a revit view where only walls and other flat elements are visible, and link that one via fbx. For smaller elements such as pipes, you could setup another revit view where only those are visible and link that one via DWG (assuming that you export them as solids). This way you would retain separate control over the tesselation of large and small objects.

 

...about units

 

Revit units are stored internally as feets. Changing max's system units as feet will get rid of the issue and improve the file link performance as no mesh rescaling has to be performed. I am not saying it is the ideal solution but that might be acceptable workarounds for you.

[Justin Hunt]

Thanks for this info, can you shed some light as to why Linking FBX creates a different mesh to importing FBX?

 

jhv

[Bruce Hart]

I don't think I've ever imported a Revit file, that wasn't a frustrating experience on some level. Initially I was exited about the FBX link in 2011, but found the curve tesselation problems as Justin mentioned (such as faces crossing one another on curved walls). The consolidation of objects by category/family is great with FBX (link), but it seems this feature is still not available in DWG format.

 

I wish you had a straight forward way of importing where you had the tesselation control of DWG and the object consolidation of FBX link, no edged faces, no invisible block headers. It could happen one day.

[pfbreton]

Thanks for this info, can you shed some light as to why Linking FBX creates a different mesh to importing FBX?

 

jhv

 

It is not but I can see why you think it is happening

 

When we file link a fbx file, we actually invoke the fbx importer internally. File Link gets the imported data in memory and performs additional tasks:

 

- it runs a routine to hide common edges to get rid of the triangulated mesh problem. Triangles do not disappear, they only get their coincident edges hidden. ((this was also one of the number one complaint about fbx import)

 

- it performs a combination (depending on the selected option) to reduce object count (this was also one of the number one complaint about fbx import)

 

- it wraps the mesh into a filelinked mesh object

 

 

However, from the memory and display perspective, this is identical to an Editable Mesh primitive object.

[pfbreton]

a straight forward way of importing where you had the tesselation control of DWG.

 

Sounds like the ideal scenario would be able to preserve revit entities as solids just like we do for SAT import in max (with Bodies entities).

[kenpimentel]

Has anyone tried exporting Revit SAT files and importing them into 3ds Max? I think the biggest issue is that SAT only really works for parts and you lose layer, material and object hierarchy - so it isn't going to work for all workflows. You will get a "body" inside of max instead of a mesh.

 

We know what the ideal workflow is, and we're working with the Revit team to solve this problem. Most of our issues come from the inability to access the Revit core objects as solids. This wasn't possible with FBX and DWG is pretty limiting for other reasons. We haven't given up, just the right solution is going to take some time. I hope you can be patient.

[Dave Buchhofer]

I've had mixed results with the SAT type, it works well for smaller models, but on larger models the import can hang for a LONG time, while trying to redraw the editable bodys i believe.

 

I just did the exterior shell workset of this current model (6 floor weird looking office building), and its been going for 45 minutes so far on a remote machine, i'll let ya know how/if it works the import worked, and i saw a flash of the finished model on the screen after 10 minutes, it then went to white, i'm guessing while it is tesselating all the curves for the viewport?! who knows.

 

right now, i'm having the best luck with FBX file link and importing with combine by material, while using the Category and Worksets in revit to export larger revit files into several different fbx's, with a couple scripts to link a whole directory of fbx's en-masse. lets me update selectively from the revit file later down the line, instead of sitting through 45 minutes of 'Combining Objects' in the fbx import.

 

a reasonable way to mass export out of Revit would be VERY helpful, started to write something to spit worksets out to separate files but its a spot beyond me right now in terms of time investment.

[Dave Buchhofer]

Its finally viewable now (56 minutes later), it works very well for the curved objects (converting them to a mesh gives you a much nicer tesselation) though still a bit heavy with the coarse viewport type.

 

I may selectively do some of the objects like this~ though i wouldn't want to do many, since it might make some things like the handrails and columns actually usable from the revit model.

 

I wouldn't do the whole model though, as there isn't any collapsing, and the materials come thru as a single giant multi-sub. collapsing several thousand objects is a pain memorywise

 

Though, the fact that the names of the objects are somewhat relative to either the materials or the family types, makes a workaround to replicate the collapsing options possible

 

HMM!

Edited September 1, 2010 by Dave Buchhofer

[Crazy Homeless Guy]

Has anyone tried exporting Revit SAT files and importing them into 3ds Max? I think the biggest issue is that SAT only really works for parts and you lose layer, material and object hierarchy - so it isn't going to work for all workflows. You will get a "body" inside of max instead of a mesh.

 

I have largely steered clear of SAT's. The current model I am working with is running roughly 56 to 58mb's as a DWG export. If I switch to SAT, that files grows to over 1gb in size. That is a scary file size, though maybe once imported it will reduce back down in size.

 

I didn't consider it as a partial workflow solution.

Edited September 1, 2010 by Crazy Homeless Guy

[Dave Buchhofer]

Travis, looking at it, the import costs in terms of time are very prohibitive, (I've set one of my rendernodes to importing a complete revit model as a SAT, and its looking to be on the order of hours.)

 

But in testing with smaller models, the geometry that is returned is a LOT nicer than the FBX/DWG types that i've played with. it needs to be post processed (Detach by ID, Weld, AutoSmooth), and it doesn't have any of the linking features of the FBX, but it might be handy for cases where ultimate cleanliness is needed. (IE: Realtime shite).

 

We'll see if it finishes by the morning

[Justin Hunt]

SAT worked best with regards to clean meshes,but and this is a big but. Being a body object the retesselation occurs at render time, which is great to get really nice smooth curves on close up objects. Not so great when the model is really complex and detailed. It becomes too heavey to render.

 

I hope I am missing something with the SAT workflow because its one of the cleanest meshes so far.

 

I am not convinced that FBX import and FBX Link are doing the same thing. I am putting a test together to illustrate

 

 

 

jhv

[Bruce Hart]

We know what the ideal workflow is, and we're working with the Revit team to solve this problem. Most of our issues come from the inability to access the Revit core objects as solids. This wasn't possible with FBX and DWG is pretty limiting for other reasons. We haven't given up, just the right solution is going to take some time. I hope you can be patient.

 

Ken/Pierre,

Forgive my frustration - I appreciate the info you guys are providing on this thread. I'm sure it's not exactly easy from a programming point of view to translate between the two packages.

[Justin Hunt]

OK I stand corrected, it is working properly with linking and importing. Was this addressed in one of the hotfixes or the FBX update? because we were having issues in the past

 

As an illustration as to what was happening, I have managed to recreate part of the triangulation issue. When an EDIT MESH modifier is added, the geometry is good. When and EDIT POLY modifier is added, the geometry is bad.

 

jhv