It’s always best to plan ahead.BIMscript
Lawrence Lam • November 12, 2019
When it comes to creating models in BIMscript, it’s always best to put a plan in place before getting started. One must first decide which inputs should be used when there are several source files to choose from—NURBS or Meshes. Here’s a quick point of difference between the two.
NURBS—get the smooth moves.
Both NURBS and Polygon Meshes are capable of producing high-quality, three-dimensional models, however NURBS generate accurate geometry with the smoothest surface. So in general, it’s always great to start with NURBS. And in Rhino, they’re way easier to handle and you can create precise meshes from these files as well. An example of NURB based source files would be files coming from Solidworks, Inventor and Catia.
Polygon Mesh—shell out a surface.
Polygon Modeling creates a 3D object non-mathematically. So it’s not as exact as NURBS, because it doesn’t average the curve points. Plus, working with meshes can be troublesome if they’re your only source of information for geometry. However, if the quality is good they can still provide great topology. Good meshes are also a good place to start. Examples of mesh files would be 3DS and STL file types.
If you’d like to learn more about the differences between NURBS and Polygon Meshes read our previous blog on why both models are needed here.
Sometimes choosing can be very complex.
Level of Detail (LOD)—to dial in the complexity of your choice there are LODs. Simplistic content just being used for collision checks use LOD100. Increase realism use LOD200. And for amazing true-to-life accuracy there’s LOD300. If you’re looking to keep the file size relatively small, LOD200 contains the basic geometries as in LOD300. It just won’t have the smaller parts within the script—such as handles, hinges, buttons, etc. These details aren’t needed in the script for LOD200.
Lose the blahs—since most models are used for rendering, it’s always advisable to lose all the internal and non-visible details such as mechanisms, holes, etc. Eliminate the particulars like screws and bolts because they add to the geometry complexity, increasing the overall file size.
Keep it real—elements that are a part of the aesthetics, like access panels or handles that represent a functional component should be kept. But again, the minutiae should be minimal.
Beating the system—let’s be honest, fillets are a pretty pleasant sight. No product in the world has perfectly sharp edges. However, in order to create fillets you need a ton of polygons in your meshes—making your file extremely large. Not to worry, there’s a way to beat the system—welding. In other programs like Blender, welding is called smooth edges.
Using either technique, you instruct the render engine to not have sharp edges. The engine then creates light and shadows over the edge instead of a defined contrast without the added geometry - thus “faking” a fillet.
Peeling back the layers.
What exactly goes into which layer? There are a lot of layers when working in BIMscript and BIMscript is very specific as to what each layer contains. Here’s how they break down.
LenaNURBs Layer - The NURBS representation of the model belongs here.
Layers without the “Lena” prefix are for Meshes and 3D hotspots.
Lena2D Layer - are for surfaces without curved boundaries and lines which are scalable (X and Y axis). They have to be placed in this layer along with your 2D hotspots.
LenaNURBS2D—these are surfaces which contain curved edges which are static or profiles used for an extrusion, they go into this layer.
Bringing order to your geometry.
Under each Lena-specific layer, you can create sublayers to keep your content organized. It’s up to you to categorize by Level of Detail (LOD). If you have different types of the object and would like to be this logic consistent, than do it!
In summary, keep these four steps in mind;
- Get the best source file to start
- Determine your Level of Detail (LOD) and delete the rest
- Place object in the correct layer
- Create custom layers to further organize your project
Sensible planning is essential to improving your BIMscript experience. To become an accredited BIMscript developer click here. If you’re looking for a BIMscript accredited developer, drop us a line at info@BIMobject.com and we’ll connect you with one. Best of luck with your BIM creation.