Some of the most widely used parametric software today is Grasshopper for Rhino. Within Grasshopper, one of the most useful additions for Structural Engineers is the ability to achieve traditional analysis similar to that available from ETABS, SAP2000, Spacegass or Robot. Having this option in a parametric program can be hugely more powerful than using the software in the traditional static way.
This post is a brief comparison of the differences between two of the most popular options of Karamba3D and Kiwi!3D for this type of analysis. Note that for many of the items it is possible to simulate analysis even though a native component is not included.
The table below compares the two with explanations of some of the items under.
Comparison Table
| Karamba3D | Kiwi!3D | |
| Members | ||
| Beams | Yes | Yes |
| Shells (1) | Yes, Meshes | Yes, BREPS |
| Membranes | No | Yes |
| Cables | No | Yes |
| Sections | ||
| Section selection (2) | Time consuming | Time consuming |
| Built-in section sizes | EU, UK, US, India, Germany, Canada | EU |
| Create custom sections | Yes | Yes |
| Analysis | ||
| Linear Analysis | Yes | Yes |
| Non-Linear Analysis | Yes (Work In Progress) | Yes |
| Vibration | Yes | No |
| Form Finding | No | Yes |
| Loading | ||
| Point | Yes | Yes |
| Line | Yes | Yes |
| Area | Yes | Yes |
| Forced Displacement | Yes | Yes |
| Temperature | Yes | No |
| Output | ||
| Rendered Analysis model | Yes, for built in sections | Yes, for built in sections |
| Bending, stress etc. diagrams | Yes | Yes |
| Support forces | Yes | Yes |
| Deflected shape (3) | Rendered | Lines / BREPs |
| Cost | ||
| Liscence | Most Free but licence required for full functionality | Free |
Notes
(1) I would consider the ability to use BREP element a huge strength over Mesh elements. This is because:
- Meshes are approximations dependent on how fine their mesh size is for their accuracy
- Generally point loads and member connections will need to line up exactly with mesh nodes. This is hard to do sometime in practice with a parametric model.
- Mesh output is not as easy to use as BREP output for displaying results
(2) I believe the method of selecting section sizes for both of these plugins can be time consuming at the moment. Not all section sizes are available (especially Australian sections which appear in neither of them). Karamba has better support for creating custom sections however not all shapes are available with the methods available and the output is sometimes not rendered.
(3) Karamba has rendered 3D deflected shapes for supported sections while Kiwi!3D does not. On the other hand, Karamba outputs deflected shape as Mesh elements which are not as useful and easy to work with as the BREP output from Kiwi!3D.
Conclusion
As you can see, both plugins offer much of the same functionality. Although I use both I have recently been using Kiwi!3D more as I find it a bit cleaner and quicker to use. However there may be times when Karamba is required as it has a few more features.
Structured Parametrics 