Revit to 3dsMax

[pfschuyler]

I have a site model in Revit which contains 18 small buildings, of 3 custom designs (several of the designs are repeated and repositioned). The Revit master site file is about 20mb in size, and the 3 buildings, all complete with construction documents, are about 11mb each. In Revit the site model is perfectly workable on my fast computer. When the site file is exported to 3dsMAX, the file size balloons about 200 MB, making it all but unusable for renderings. I've tried both the dwg importer and file link manager, and every option I can possibly think of within both, and nothing seems to reduce file size. I have systematically tried all of the import options one-by-one. There are options that affect file size, but not significantly. I wasted hours and hours on this, and I have nothing to show for it.

I've avoided importing trivial detail like plumbing fixtures. I am also aware that I can box out a portion of the model via Revit but I really don't want to do that because I am looking specifically to do site renderings. This is not an unreasonable size project, at best it could be referred to as mid-size. The Revit-Max route apparently can't handle it.

One would think that the Revit models, complete with pages and pages of detailed notes and drawings...would be larger in size than the imported model in 3dsMAX. But they are not, even an isolated building gets considerably larger when going from Revit into Max via the coveted DWG translator. This affect is magnified many times over by multiple buildings.

Has anyone had this experience?

Paul Schuyler

[Steve_Bennett]

I hear your frustrations! You're not the first to come across this issue, in fact others have had it happen on just a curtain wall, but that won't help you. Here are some things to try.

The main thing to remember is that when going from revit to max you are entering a different program platform and different rules apply. First, you are no longer doing construction docs - you are visualizing your scene. In hollywood, nothing is behind those walls on a set. Same principle should be applied in MAX. Get rid of things that you will not see in the rendering. Second, face count (polygons) is everything in MAX - especially on a 32-bit system. You mentioned that you have a fast system, but not the specs. In the past (and still is to a point), it was more about RAM than processor speed that affected how much data you could load into a scene. In a 64-bit platform you can throw as much ram at the problem to help, but that's not always the answer. helps to understand the why before throwing more money at the problem.

In revit when you perform your export, go into the options and choose to use ACIS solids instead of polymesh for exported 3D objects. Currently if you are going from revit 2008 to MAX 9, your materials won't come through perfect, however you will greatly reduce the file size on export. The MAX dev team is working on improving this for a future release of MAX.

Also in revit, try setting up a standard layer export for your layers. Something that places interior objects on separate layers from exterior objects. Then, once the file is exported, open it up in AutoCAD first, and clean out any unnecessary objects that you will not see from the exterior of the buildings in your site plan. Purge, audit, purge audit and save/close the file. Then in MAX choose link or import.

If you have trees or other plants/shrubbery in your revit file, do not import/link that into MAX. In MAX you should be using shrubbery native to that platform to reduce your polygons in the scene.

Another way is to get into texture baking, a process which permantly places the detailed features of an object - such as the side of a building - onto an object with one face such as a box to replace the millions of polys used to build the building. The process is quite detailed, so its hard to get into with one post.

Another thing you can play with on the max side of things is under the Derive AutoCAD Primatives by: - those settings can help optimize your import of objects, but typically you need to have a cleaned up dwg file before getting into other settings than the default chosen for the Revit preset.

Now if that still does not work for you, then you will have to go even more advanced. You will have to export each building model from the project to its own dwg, then clean it up, then link it in. You may need to get into compositing, rendering one pass for the buildings, another for the terrain, another for atmosphere, another for effects, etc. and then combine them in a compositing software such as Combustion.

I guess the main thing I am trying to convey is that in all these sweet eye candy videos and pictures you see, it is never just export, import, render, done - much more is involved - something especially true if working with something on the scale of a site plan. For the more mainstream visualization companies, its easier for them since they have been doing this a while but often those who have not dealt with MAX before don't realize the amount of work that can still go into this process. I hope this helps you understand the situation better!

[hand471037]

Another problem I've run into in the past when trying to render very large Revit models (i.e. skyscrapers) is that Max doesn't seem to like the way that Revit makes blocks.

Revit outputs many, many small blocks that are all slightly different from each other. Max doesn't like having many, many small blocks and chokes on this.

We found that exporting to DWG and exploding all the blocks and then purging and auditing the model, and then pulling that into Max for rendering worked better. Or converting the DWG or DXF into an STL and then importing that.

Either way, however, with very large models you're going to have to do some work either prior to or after importing into Max in order to get what you want. You can't expect to simply export your Revit models and hit a 'render' button and have it work when dealing with very large models.

Think of it this way. Had you modeled the whole thing in Max to begin with, you'd still need to do a lot of things to manage that model and make it workable just due to the size.

So you might need to forgo using the 'link' between Revit and Max, and just export the model from Revit and work it over for Max instead...

[pfschuyler]

Steve,

You threw in everything but the kitchen sink! I'm a bit frustrated because this process should be easy, instead it just doesn't work out in any simple way. I do appreciate all the workarounds but I believe we are dealing with some software issues here. Regarding specs, I have two machines; one is an Athlon X2 6000+ with 2 gigs of Ram, running Windows XP Pro and a FireGL card. The other machine is an MP server running 2 5050 Xeon (dual core) 3 ghtz CPUs, 64bit XP, 4 gigs of ram, and another FireGL card. Both machines have 10,000 rpm hard drives.

When importing my Revit model into Max with the ACIS solids option, Max crashes every time. Scratch that option. That's with the latest productivity booster and service packs installed. Layers are pretty clean and well organized, with no extraneous stuff coming in. Extra detail like plumbing fixtures are not imported. Most railings are changed specifically to be non-circular in section to reduce polys.

I do not believe this is a polygon issue (I'd give you a count but I don't want to open that beast up right now). I realize polygons are important in Max, but a model of this size should not really be an issue compared to what advanced users out there are doing. There is a specific problem I believe with this DWG import option carrying a bunch of extra dead data along with it. If I take the same exact model from within Max, and export it to OBJ piece by piece, and import those models into Vue 6 Xstream standalone, Vue can handle the entire site without too many problems, and Vue can even compress the complete scene down to 40mb. That's a much smaller file for the same number of polygons and materials, plus additional information in there like atmospheres, ecosystems, etc. Unfortunately that is a long tedius import and export process. Plus I specifically bought Xstream for rendering out these models from within Max, to make things fast and easy.

Generally Max is quite stable and robust but I am 100% against this DWG import option. Autodesk sells this like its an extra feature we should all be thankful for, but in my view its simply a questionable attempt to leverage markets using the DWG format. Why not add a OBJ exporter for Revit? Or FBX? Or 3ds? Autodesk owns them all. I do believe they do not add those features because that would make a number of other rendering/modeling options very compelling for us Revit users. Instead we get Max or Viz, take your pick.

Sorry to rant, man. But I'm looking at an extra $4000 worth of software that only seems to be making my life more difficult. I can probably handle that. But after all of that work and extra software education, here I am facing a deadline that is about to blow up in my face (this afternoon). That I do not appreciate. Perhaps when Max 2008 comes out soon I might be able to get something done with this, we will see. Anyway, nothing against yourself, thanks for the reply.

Paul S.

[pfschuyler]

I do appreciate both of your responses and admire your tenacity to pursue workarounds. But I beg to differ in this case. With a model like this, it should definitely be as simple as importing and pushing render. After all, once you can do that you can begin to invest your precious time enhancing the model and making it truly spectacular. Pushing render is just the starting point to having a workable scene.

The Revit files themselves contain more useful data for sure. All Max needs are polygons and material assignments (heck, toss the UV's I'll do that manually). These files should be much, much smaller and it seems to me there is something wrong with the DWG format and this process of translation.

I really do hope Autodesk is listening. But thanks again to you both.

Paul S.

[Steve_Bennett]

I see your point about it should be easy, but in fact this is a process that has only begun to take shape in the past couple of releases for MAX when dealing with Revit models. Yes, the dwg link/import has been there for some time. However MAX has always been built around the gaming industry which has low polygon models. It has never been built to handle both large numbers of objects and high poly counts. I spent some time with one of the Design Viz (DV) AE's from autodesk the other week and he mentioned this is one thing they are working on for MAX. So yes, they are listening. He came from the Architectural industry and dealt with the firms DV department and getting models out the door for projects. So he knows the pain we face out here and has spent some time trying to help the dev team for MAX understand this. Another unfortunate thing is that we are looking at 2 separate dev teams - 1 for revit and 1 for MAX. Add to that the fact that MAX has been on a different release cycle than Revit and you have the perfect recipe for keeping 2 teams from talking to each other. Not an excuse - just something they need to deal with. Change is coming - just not in time for your deadline unfortunately...

:beer:

[pfschuyler]

Steve,

Thanks for the professional reply, and I apologize for my anti-autodesk rants. I managed to get through my deadline intact for the most part, and I look forward to the new features in Max 2008, which I think might solve my problem or come close to it. A 50% reduction in file size with ACIS will go a long way to making this basic scene of mine workable. Fact is I don't plan on doing anything much bigger than this in one file. I do wish Autodesk would consider some other options to the DWG translator though...Revit is outstanding, and so is Max, but choice is a good thing.

Paul Schuyler

[Steve_Bennett]

Steve,

Thanks for the professional reply, and I apologize for my anti-autodesk rants. I managed to get through my deadline intact for the most part, and I look forward to the new features in Max 2008, which I think might solve my problem or come close to it. A 50% reduction in file size with ACIS will go a long way to making this basic scene of mine workable. Fact is I don't plan on doing anything much bigger than this in one file. I do wish Autodesk would consider some other options to the DWG translator though...Revit is outstanding, and so is Max, but choice is a good thing.

Paul SchuylerYou're welcome and no worries on the rants. Sometimes it just feels good to let it out... :beer: Besides, I don't work for Autodesk. ;-)

As I get tied in more with Autodesk, I'll be sure to bring up experiences like to help them understand what is going on. I agree that the options in the DWG translation process still need refining, but slowly it will get there - I'm sure of it. They can't remain stagnant. I've heard of other plug-ins used with MAX in conjunction with models containing high poly counts. One such thing used was the chaching feature of v-ray. Something to consider when you have some time to look into it.