This article discusses some of the key elements in successfully integrating and managing the interrelationship of Autodesk® Revit®, Autodesk® 3ds Max®, and 3D Printing.
Way back in the old pre-BIM days, the task of creating a 3D computer model for visualization purposes was complex and laborious. Now, for many projects, that 3D model is a gift that comes from the act of creating plans, sections, and elevations in Revit. So, rather than importing 2D reference drawings into 3ds Max Design and creating new 3D entities, we are simply importing that model. The complex, time-intensive task of creating a 3D “wireframe” model has been eliminated. So how can we make the best use of that gift in 3D?
For high-quality study images, one can stay within Revit itself and dispense with the whole step of exporting and importing. For more sophisticated visualizations, going into 3ds Max Design is a necessity. The benefits include greater control over the look and feel—the ability to create an animation or panorama and to visualize the project within its context whether that be photographic for photomontage or texture-mapped geometry.
There is an often overlooked second benefit which should be planned for when the decision is made to move between Revit and 3ds Max Design. This is the 3D Printing (3DP) of the virtual model to produce physical, real world models. 3DP models are really physical instances of the virtual model. The ease with which a 3D model used for visualization purposes can be used for 3DP can be greatly enhanced if one is aware of those needs.
The first and most straightforward item is to export as Solids from Revit as opposed to Polygons for DWG files. Visualizations tend to be stage sets where faces of geometry not seen from a viewpoint can be eliminated. This helps speed up the processing time for a rendering. From the 3DP perspective we end up with a model that needs to be rebuilt as solids in order to be reused for physical model creation. While many 3DP projects may start from this point, planning ahead saves much labor time. It’s always good to recycle data rather than reconstruct it.
Figure 1: Revit CAD export
Texture mapping and the design of the 3DP model itself are also very important. There are assets such as cameras, lights, and animation tracks that intuitively aren't involved in the conversion to 3DP. Even though for color 3DP we export a VRML file from Max Design that may contain some of this information, once that file is brought into software for checking and printing the 3DP model, that information is ignored.
Figure 2: Revit VRML export
There are also plug-ins and shaders, which many renderers use to get the look and feel they want. None of these effects come through for 3DP. Not only do the lighting effects not translate, but any materials not of the standard sort don't either. So, if you have mental ray materials, they need to be redefined as standard in order to appear on your 3DP model. 3D printing of texture maps in full color is desirable for most of my projects and I believe that this new aesthetic is growing in acceptance. It is highly recommended to test-print small, almost 2D pieces with your texture maps before printing the final, larger pieces in order to nail down the look and feel.
Figure 3: 3D Printed model
Within our standard material limitation, we are able to use Multi/Sub-Object materials that are very helpful when using solids. Otherwise it would be difficult to have a wall with different colors on one side or the other. It is wise to test this first before going too far as I have had some issues in earlier versions with maps not sticking.
3DP-specific software such as Z-Edit Pro allows for colors to be defined with them, but we really want to do it all in 3ds Max Design if possible. Imagine needing to make some changes to your model, needing to export a new VRML file and then having to go through color changes again in the 3DP software.
Figure 4: 3D Printed model
Now let’s get into how to design a 3DP model. There is no “easy button;” this is not an automatic process. Woody Allen's movie Sleeper was not a predictor for the future, but rather satire. Efforts to make the process more intuitive are needed and are being developed. However, to lose control of the final product is not something in which those of us at the design end of the AEC spectrum would have much interest. If these developments are able to produce a good first pass of a model design from which one could customize as needed, that would be as good as it could get. It reminds me of when CAD was starting and hearing some architects comment that the next version will have a better interface design and, therefore, not be difficult to use. Well, 20 years later, a certain level of skill and commitment is still required to create and produce with CAD or BIM and that will always be the case.
Those who have direct access to a 3DP machine have an advantage in design 3DP models. Since these are all tools, if you don't know your tool, it makes things more difficult. To create elegant solutions, you need to know the limits. The aspect of fragility pertains more to the processes internal to the machine like depowdering and handling during infiltration than to the finished product itself. We create very thin elements in our models, but understand how they need to be handled en route.
Figure 5: 3D Printed model
For example, I recently finished a project of an office tower that had very thin floor plates. 3d printers all have size limitations. Our projects don't necessarily respect these boundaries so we quite often make models from multiple pieces. The trick is to hide the seams. Luckily the precision inherent to this medium works in our favor. This project had five sections of about eight floors each. Each one was printed vertically. I slipped thin cardboard underneath to move it from the machine and do the final depowdering. For the infiltration step, I brushed cyanoacrylate (SuperGlue) on the edges of the floor plates. This way I could handle it then dip the whole piece into a bath of the stuff without breaking it. The result is super-thin yet strong pieces that were not thickened for presentation purposes but true to size, which is important in maintaining the audience's interest and lends legitimacy.
Figure 6: 3D Printed model
Just as 3DP model creation on the software end needs to be an integrated approach, the same is true on the output end. Hybrid models using traditional materials as well as 3DP is often what the project calls for. We have had success in designing the whole model in 3ds Max Design and then going to 3DP for most elements and for other ones to derive the templates from that computer model. This way, the exchanges with the clients during the process are realistic and, in the end when it’s built, the surprise factor is eliminated.
Maximizing the life of the Revit model in the visualization of our projects—even into the physical model creation realm—brings fuller, more accurate, and less expensive production efforts. 3DP models are the reincarnation of visual models in the everlasting life of AEC visual communication.