Strange Models exported from Revit...why?

[raphael.dunbar]

Does anyone know why the following happens? If I create a wall with 2 windows that are parallel in height, and export to 3ds max via .dwg, I get a model in max like the first row. If I do the same in ADT 2005, this does not happen as can be seen by row 2. But if the windows are NOT parallel in height (in Revit), and export to max the model behaves normally, as can be seen in row 3.

Can anyone explain to me why this happens, and how to correct it?

[aaronrumple]

Unfortunatly in the shaded views you've shown we can't see the triangulation. You should be able to edit the tesselation in Viz and correct the issue.

[raphael.dunbar]

I have added a pic that is alot clearer, showing the wireframe and triangulation (I normally have edge triangulation hidden - through driver configuration). Aaron please could you expand more about editing the tesselation in Viz/Max. Do you mean editing the model manually, adding vertices etc, or some more automatic method? I was rather hoping this problem could be fixed before exporting to Viz/Max. I did find an option in "Type Properties" of windows, called "Wall Closure", with the options by host, neither, interior, exterior and both. But they do not seem to affect anything.

RD.

[aaronrumple]

The way top "fix" it is to have the design complete before exporting so you don't have to manipulate it in Viz. Yes you could manulally edit the mesh in Viz.

[FK]

I understand the rows in your illustration. Could you explain the columns? Are you trying to make the wall thicker by dragging its face? It seems that in the weird case someone dragged the little rectangle between windows, instead of the entire wall face.

Never touched Max myself, unfortunately...

[aaronrumple]

If your are trying to make the wall thicker in Viz, you only need to do an edit mesh and make sure you've selected all the planes of the wall prior to moving them to the new location.

[raphael.dunbar]

Ok, let me explain. I'm trying to show that the models exported from Revit are poorly constructed, and that there should only really be one face to the wall not 2. By pulling out one of the faces from the Revit model I was trying to show that there are overlapping edges. This can be clearly seen between the ADT 2005 and the Revit pics above. ADT 2005 is producing "clean" models. However in Revit, this "problem" only occurs if the windows are horizontally parallel, if the windows are not parallel the model is exported as expected, just the same as the ADT models. Why is this?

I have also included some line renders done in 3ds max, from 2 models exported from Revit, and 1 from ADT 2005. Line renders are dependent on good clean models to get good results.

[hand471037]

Revit exports everything as a polyface mesh. It's not 'wrong' or even a 'problem' or 'unclean' models, it's just a polyface mesh. As such, there is probably some extra triangulation going on when either it's exported or when it's imported into Viz/Max.

I used to solid model everything in AutoCAD and then export that, via 3DS, into Truespace. When the models were brought in there were always extra faces and triangulation you had to deal with.

I think this has something to do with the fact that most 3D programs, upon export, make the data as simple as possible, i.e. they triangulate it, so that anything can read it. Multi-vector faces (i.e. that face of a wall you've got there) are handled differently within different softwares I bet, so maybe that's part of it too. So probably, since ADT and Viz have been owned by the same company for longer than Revit and Viz, they understand each other's models better and less simplification has to occur. That's my guess. I mean, we've just now seen some minor level of integration with Revit and Viz, and I bet we'll see more next year.

But to say that Revit doesn't produce clean models because they don't open 'clean' in your software package is a little silly. The real issue here is that they need to add a better export out of Revit for 3D needs, i.e. a 3DS export or better exporting to DXF that doesn't render everything as triangles...

I export models into Blender, AutoCAD, and Radiance and have no issues at all with the models (other than Blender no understanding Revit DXF's for some reason, so I have to export to AutoCAD first, for now).

[raphael.dunbar]

The real issue here is that they need to add a better export out of Revit for 3D needs, i.e. a 3DS export or better exporting to DXF that doesn't render everything as triangles...

Yes I agree with of what you have said, a 3DS file export would be a great feature to add to Revit.

But in the mean time is there anyway to control this extra triangulation going on when its exported from Revit? As in, can I change some settings inside Revit? Plus why does it only happen when you have windows or doors that are positioned at the same height?

I also do see this as a 'problem', because if I want to do certain things with the model, in Max, its going to take me a long time to fix the model.

RD.

[hand471037]

wasn't saying that it wasn't a 'problem', it is, but the problem is with both Revit & Viz/Max...

anyways, how are you bringing these things into Viz/Max? As a DWG? Have you tried DXF instead? I haven't used Viz/Max in a long time, but I remember there being a ton of import options for both when bringing in DXF/DWG's. Or do you just link in the DWG? Maybe some of those can solve the issue, rather than for there isn't any control over this within Revit itself & it's export function...

[aaronrumple]

Still think any cleanup could be done in Viz/Max with little effort. Tons of tools there for simplifying meshes.

Revit has it's own 3D engine. How it triangulates is up to the programers. For any export option, I'm sure thay have tried to preserve detail over streamlining the DWG output.

[raphael.dunbar]

Aha! Ok, I have some good news, playing around with smooth groups, I have managed to eliminate the problem, that the models where causing me. I'am sure, I tried this before and it did not work, ...but hey I'm happy now :)

Thank you all for you comments, help and advice ;)

RD.