Revit BIM model for high quality renderings
Author: Vojislav Ninković | MSc Architectural Engineer | NS Drafter
A demand to respond
In the past 20 years, BIM has changed the AEC industry in a way no one couldn’t predict. BIM stands for Building Information Modeling and basically is the environment for 3d modeling in a case when a building model represents an Information database of building elements. Although many countries have already introduced a legal obligation for BIM usage, implementation of BIM might seem less attractive because of employee training along with funds that should be set aside for software purchasing and often for hardware performance enhancement. For this project, our company was using one of the most wide-spread software for BIM modeling – Autodesk Revit.
Rather than just as a composition of different building elements, we prefer to think of the whole building model as a large Revit family. What I mean by this is that there are some initial parameters to be set up before taking any action. Just like setting reference planes, it starts by defining grids and levels that all of the model geometry would be attached to so that if there is any need for a change – it can easily be done by moving the planes only.
Importing and linking CAD files
Under the assumption that working on almost every BIM model contains importing some CAD drawings, it is important to note that they have to be aligned with the axis and pinned after importing. Furthermore, the select pinned elements option can be enabled so that the CAD underlay can be selected (surely it cannot be moved because it is pinned). In case the model and the background overlap (if the drawing is overloaded), the background can always be selected and isolated if it is necessary to take a closer look at it. Also, if you work on the slab’s contour, for example, you can go down to the level below through the view range and compare the contour of the slab with the walls of the previous floor.
Basic workflow
A well-organized interface and a wide range of tools in the toolbox work fine with most of the demands. Both system families and components cover lots of cases, but unfortunately, not all of them, so that you will often have to put some extra effort into making some specific elements, in this case, windows and storefronts. The rest of the model wasn’t that specific, so using standard tools was luckily quite enough. However, there are some deficiencies inside Revit, causing the struggle.
Working with component stairs inside the Revit environment is conceived to start with defining the base and the top-level and setting up maximum step height, minimum tread length, and minimum tread width. Right after, the number of risers can be adjusted to get the desired slope and the actual tread depth to get the desired stair length. When you set the first point and start pulling, Revit will let you know how many steps are left. Each component (run or landing) has its own control arrows for modification and control points, which add or remove steps. Things are starting to get complicated at the moment for fine-tuning the first and last steps when you realize that raiser height can not be changed individually.
Similarly, whoever has experienced modeling of coverings in Revit, knows how wearing it could be. An impression of all elements already being made and visual confirmation in the form of the model’s overall look could deceive even experienced professionals and make them believe that the modeling process has come to an end. Whether it’s walls, floors, stairs, or some other element, not only that placing of coverings demands more time, but the editing of contours often does, as well.
Speaking of walls, Revit forces users to start with modeling of walls, which will be used as wall coverings, and then allows joining them with primary walls as a separate process. Additionally, it might also take editing of the wall profiles step. When placing walls, Revit will offer us a few standard options, such as pick lines and pick faces. Our Team members find those options very useful for placing coverings, especially when combined with allowed join status, but facing the fact that none of the Revit-embed functions would show up with a different approach, led us to look the other way for a long term solution. With a lack of Dynamo experience, giving ourselves a try was perceived as even more time-consuming at the moment. Still, once we bumped into WallFinishesByRoom script, as a part of ModelicalDynamoPackage – our needs were finally satisfied. What this tool basically does is reading information about wall coverings from the room schedule and using it for placing new walls above room bounding ones. Besides that, it automatically joins them together.
Making changes, in general, is something you should be prepared for. With that in mind, you want to make sure that all of the wall coverings at the staircase are broken at appropriate places, just to make sure that if you want to change some covering later on – that change doesn’t affect the rest of them.
Basepoint for realistic renderings
When it comes to making 3D renderings, the collaboration between a detailed Revit model and 3ds Max (a traditional 3D modeling tool) is maximally synchronized for a great result. Skipping all the downsides and weak points of 3d Studio, a user practically finds himself dropped into photo finish, giving the model only the final touch. As Max natives, we have tried various render engines out, and currently, Corona Renderer works best for us. Despite all the materials that need to be changed, because the Corona Renderer engine won’t recognize Autodesk materials, relations that are predefined inside Revit will still save you hours. 
To summarize
Setting as many parameters as it is necessary for making changes easily should be a priority when considering parameter detail level. Conditions for a highly parameterized model that Revit surrounding offers are excellent, even though they can sometimes become restrictive. Material parameters are useful, not only for material take-off and cost calculations – but for making renderings in outsourcing software, as well.
