Streamlining BIM workflow for Unity HDRP application development

Posted by Kate Barlow on 14th March 2019

Common Problems with BIM Models

I receive a BIM model of a five-storey building from the architect and at a first glance everything looks great. Geometry looks ok and it’s running at a good framerate in editor. But when I start to replace the materials, problems start to pop up. There’s a wall-object running through the building and when assigning material to the living room wall, the editor puts the same materials onto the walls in the kitchen and the bathroom as well.

I want to replace the bathroom wall with nice ceramic tiles and the kitchen needs its own materials too. Oh, and wait! There’s a solid floor slab running through the whole storey. I can’t have oak parquet in the living room and a stone floor in kitchen without manually separating the rooms. On and on; new problems start to appear. It looks like I am going to be spending next week cleaning and fixing the model. Or maybe it’s going to be easier to model the building from scratch? Not to mention that there are couple hundred rooms to light.
Sound familiar? The good news is that this doesn’t need to be the case. With only a little preparation, architectural models can be very useful – and they do not need to create any extra work.

Preparing the BIM model for virtualization in BIM/CAD modelling tools

When I say preparing, I mean that the BIM should be modelled according to good modelling practices, in line with the instructions from the Building Smart Organisation (https://www.buildingsmart.org/).
This doesn’t necessarily mean much extra work for the architect and it delivers a further benefit. A good model will produce a good foundation to create a digital twin that can be used through the building’s life cycle. It also means that you’ll get the best possible use from the Tridify BIM Tools, coupled with a smooth workflow. By investing a little extra work to create a good model, your turn your model into a valuable asset that will have lots of use cases in the future.

Here are the five main modelling practices to check when receiving the BIM model from an architect:

  1. Every object should be marked as an appropriate element type i.e. the doors should be marked as ‘door element’, walls should be marked as ‘wall element’ etc. This will enable fast and robust object finding as you can select objects by type, and, for example, you can easily create colliders or remove unnecessary ones.
  2. Multi-storey buildings should be separated storey by storey. Each storey should contain a ceiling, floor slabs and everything between them. Architects’ models usually don’t contain ceiling elements so in Tridify we generate upper floor slabs as ceilings for visual purposes.
  3. All objects and structures should be placed on the correct storey. Our lighting algorithm takes all the structures into account when you create floor lighting with our tool.
  1. Wall connections should be connected according to surface materials. This enables the visualisation of different materials on each wall section. If the walls are not connected correctly, the wall material layers will be visible on the end of the wall. The model should provide separate material layers for each room’s wall elements i.e. a wall that continues from the toilet to the living room might require a ceramic tile for the toilet wall and plaster for the living room wall. There are a number of other examples which, when not modelled right in first place, will require lot of extra work later.
  1. Exterior walls need to have proper material layers and the material layers need to have thickness. This provides the opportunity to specify walls (exterior and interior layers) in different materials (i.e. brick on the outside, plaster on the interior). If all the exterior elements are typed as external objects, you can extract the shell of the building without any interior objects.

Following these modelling practices will give you a very smooth workflow from architect model to Unity. You will find more detailed BIM modelling instructions, on our website https://www.tridify.com/support/

Why Tridify uses IFC, what is it and how get it

IFC (Industry Foundation Classes) was developed to ensure a smooth BIM process and it has become the standard in the BIM workflow. IFC can be exported from any major CAD software and it allows anyone to exchange their digital models across different software. In practice this allows us to combine data from different sources and use the same methods to access the data. IFC allows us to import to Unity architectural models from ArchiCAD®, HVAC model from MagiCAD® and furniture models from BIMobject® with the same workflow.

This flexibility is the reason we chose IFC as the input to our service. Because we have the data available, we can automate repetitive tasks.

Unity workflow using BIM data and automate HDRP lighting

There are a number of time consuming and repetitive tasks that can be significantly speeded up by scripting using BIM data. These include assigning textured materials to right elements, lighting the rooms, assigning colliders and many others. With the following process we can cut the development time and focus on adding interaction to our applications.

  1. Use Tridify Cloud Service to generate Unity usable optimized geometry. Create a new Unity project using High Definition RP template and install Tridify BIM Tools from Asset Store. Login to your converted projects in the Conversion Projects window and load your building to the scene. You can upgrade project materials to HDRP Materials with Unity command. Save the scene.
  1. Use Tridify’s Lighting Tool to generate emissive light planes and light probes. Bake Realtime GI lightmaps. Create HDRI Sky Cube map to add environment lighting to the scene.
  1. Use Tridify’s Material Mapping Tool to replace all the original materials in the scene with HDRP ones. Tridify includes some common materials to get started with. Save your mapping file for further use.
  1. Use Tridify’s Search Tool and search and select floor and wall elements. Add mesh colliders to selected objects. Furnish your building model and add camera controller to your scene. Now you are ready to build your application.

Using this workflow will spare you from routine cleaning and remodelling work. For more details you can download our manual at https://www.tridify.com/wp-content/uploads/2019/03/How-to-use-Tridify-BIM-Tools-in-a-Unity-HD-Render-Pipeline-project.pdf or take a look at our Tutorial: https://www.tridify.com/support/tutorials/how-to-use-tridify-bim-tools-in-a-unity-hd-render-pipeline-project/.

Juhani Korpinen
CTO, Tridify.

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