Binding, Revit Links, and Export to DWG

[dc.109967]

BTW, we are using RA 2008. We have a file that of a multi-family housing project that is composed of:

Topography &
Linked Revit Files for (6) unit types.

The 6 unit types are arranged in various ways creating a complex of 116 total units.

We need to export the model of the entire project for rendering purposes, etc. When I exported the project, two things happeend:

1. Revit exported the 6 unit types as individual instances so we now had 116 dwg files!!! One for each unit, even though many of them are copies of their type's original prototype.

2. Revit crashed after the 116th and final export.

Our next option was to bind each revit file to the master file. This was an absolutely horrendous nightmare. The first unit we did took about 5 minutes to bind and there were walls that needed to be readjusted and columns were jacked up as well. 10 more minutes fixing that. The second unit we tried to bind just disappeared.

This is not good, needless to say.

How are you guys dealing with this issue?

Will we have to create a new overall file and instead of linking each unit, bring it in as an import? That will take time, but hopefully not as much as binding. This is very frustrating. We are all done with the Revit work and only need to do a simple export when this happens.

Any suggestions please?

Thanks.

[Calvn_Swing]

Unfortunately, Revit has not got this part figured out. We've got a project that has 5 linked files, but only one instance per linked file. What we did was export to dwg each file individually, and merged the files in 3ds.

Just FYI, you don't want to export all the data in Revit to 3Ds or any rendering program. Think of it as WAY too much info. We created custom 3D views with the help of the people doing the rendering. They told us where they were going to place views, and what they needed to show, and what not. We were just doing exterior renderings, so the 3D views we exported from had the interiors turned off, along with all the structural information (we had no visible structure - it was all clad on the exterior). In your case, I imagine there will be a limited number of cameras. The best thing to do is plan where you want to place cameras and only export exactly what you need.

Then, export one model with NO interior information at all, just the exterior. This file can be used for all your exterior renderings.

Then, create several files that have the visible interior geometry and the screening exterior geometry. You only need a few rooms and their exterior walls. You don't need anything else.

Once you set up your cameras in 3Ds, you can copy them between all the files.

Now, when you render your interiors and there is a view of the exterior (through a window, or door, or balcony) you can render the same view in the exterior file and use Photoshop (or a more sophisticated compositing tool) to combine them.

You can do the same (in reverse) for the exterior shots. When you have a view of an interior through a window or opening you can render that interior and composite them together.

All your renderings will go MUCH faster, and because of it you should be able to do higher quality renderings.

Personally, I wish that when you made a perspective view in Revit, that Autodesk would write a different export tool specifically for exporting to a nicer rendering application. It would be relatively easy to have the camera in Revit do object culling (turn off any element in the view that wasn't visible) and then make it so that an export would include elements in linked files in the one export file) This view could then be opened in 3Ds and once materials are assigned it would be ready to render.

There are two ways to do the culling too. One way is to compute a volume that represents the camera's view range, and include any element that intersects that volume. This is the dumb way, but effective enough I guess. The COOL way is basically like a raytrace calculation. The camera sends off "rays" and any object that recieves a ray gets exported. This method is far more accurate, and exports far less geometry. Anything behind a wall is automatically removed, anything that is visible through a window is kept (because transparent things allow rays through!)

Then Autodesk could take it up a notch and include the same tool in a walkthrough! You run the walkthrough with the export tool on, and any object that gets a direct ray hit is marked and included in the export...

It would be so simple. Have a Yes/No parameter called "export for rendering" with a default value of No. Then, set up the same raytrace engine accurender uses and set it running. It would be relatively quick too as you are looking for direct hits. No bounces to calculate. You do have to make sure to set any objects with transparency to pass the ray through and include the elements that the ray hits after that. Anything that gets "hit" sets the parameter value to yes. Given, coding that last little bit would be tricky, but come on!

Sorry, I'm making myself drool now...

It probably won't happen till Revit Architecture 2020 at which point it will be useless because we'll have such computing power that having all the objects isn't a problem, not to mention that we won't be doing photo realistic renderings. We'll be giving photo realistic interactive walkthroughs in virtual space. Oh well...

[dc.109967]

Great post. Sounds like we're going to have to muscle this thing to get what we want. What a shame really. I keep trying to sell Revit to my boss as a viable alternative and when things like this come up it just gives him more ammo to say, "Screw it, we're sticking with AutoCAD."

I love your culling idea by the way.

Maybe you should go work for Autodesk and straighten those knuckleheads out?

[Calvn_Swing]

Well, in terms of muscling it, it shouldn't take too much time to do. If you really just want it all in there, you can open your rendering application and merge all 116 files.

The problem on Revit's side is that it always exports linked models as an individual file.

The bigger issue is on the rendering application side as Revit just has too much data for an effective rendering.

Can you give me a little more detail on your project? There may be ab easier way to do what you're wanting depending on how your file is broken up. Basically, I am wondering what all is in the unit types, and what all is in the host model. Depending on the answer it may or may not be an easy fix. (The walls screwing up and all).

To follow up on the Bind vs Link thing...

If the walls and columns are messing up because, once "bound" to the model, they are now automatically joining with other elements (which I suspect) you can fix that fairly easily. Open up the linked file and any wall that is messing up you can select (individually) and right click on the little blue dot and choose disallow join. Reload the link and when you bind it again those walls should be fine. I believe there is a similar function for the columns. Once you've got one of each of the 6 types properly bound you should be able to delete the links and replace them with the new groups you've created.

Not that this will help convince your boss of anything, you made a mistake bringing the files in as Links. Not that you could have known it from the get go either. If you ever want to export to another format sans the 166 files, you have to load as groups and copy the groups around. That's the trick. So, you have to ask yourself before you decide to link or group whether you want to export it (like to render it).

My rule of thumb is that Links are good for situations where you don't have multiple instances, or when the element is just too large to be grouped. So, I'd always have unit configurations and even small single residence buildings that are being repeated brought in as a group. If it were five identical 25,000 square foot commercial buildings, I'd still probably group them unless they were quite complex. Revit's magic number is 10 MB. Anything over that sparks a warning that your link should stay linked and not be grouped. Depending on your intentions and the number of repetitions, you might push that limit a bit in either direction.

If you had linked in your files as Groups originally, you wouldn't be having this problem now. It would export as one file, and you'd be off and running. (though still with way too much geometry for the rendering process and a whole lot of cleanup going on in your rendering app.)

Good luck!

[John Anderson]

I also am having trouble exporting linked files.

When I export my site with 35 linked buildings, the linked buildings walls did not show up, though stairs, fixtures, etc. did.

Autodesk has duplicated the problem and sent it to development. Heard nothing yet.

Tried the bind thing, but after 3 days of prompt-run for hours-prompt I had to crash it and get that computer back. I will be exporting the site and buildings separately and xref both into a new file and rearrange the buildings there. And yes, each building has design option variations so all have to be exported individually. Sure hope Autodesk gets back to work on the campus type workflow.

[dc.109967]

Our project consists of 116 units. There are 6 unit types: bedroom count is different on most, some are flats, some are split levels, some are 2 levels; one type has a roof deck as well.

Each "building" is made up of 3 - 5 units stacked on top of each other. All of the buildings together make up the entire project. Each building varies in that it may consist of two flats and split level, or another building will have a split level, a flat, and then the unit with the roof deck. A 5 unit building is usually 2 split levels, 2 flats, and and a 2 level type.

I hope that makes sense.

I think you're right on the walls and columns messing up due to them trying to join one another when they're bound. I'll try what you suggested and I think it should work.

John, I never got to the final export as Revit kept crashing after the last unit export. I assume that the last dwg it exports is the overall site file, with xrefs to the other 116 dwgs.

By the way, I opened a few of the unit dwgs in AutoCAD and Max, and they look great by the way. We have a kid here in the office who is a max wizard, and I could have him "recompile" all 116 dwgs into one site model, but I don't want to ruin his day.

Thanks.