What are T-Splines? And how can I use them?
Autodesk created a new paradigm in organic surface modelling with the implementation of ‘Freeform’ T-Splines in Autodesk Inventor 2015.
In this post we will explore what T-Splines are, and consider how we can use the ‘Freeform’ tool set in our daily workflow.
So what ARE T-splines?
T-Splines are a combination of Nurbs and Subdivision modelling that was developed by Matt Sederberg’s team back in 2003. The T-splines technology was originally released as a plugin for Rhino. It has also been released as a plugin for Solidworks.
In 2011 The T-splines company was bought by Autodesk and was built into Autodesk’s flagship cloud hosted 3D Modeller ‘Fusion 360‘. Autodesk Inventor 2015’s ‘Freeform’ toolset is the first time T-Splines have been integrated into Inventor.
The Inventor & T-Splines product teams have done a great job, although I’m a little disappointed that not all the T-Splines tools have been implemented in Inventor – yet!
So what are Nurbs surfaces?
Nurbs surfaces are created from a network of Nurbs Splines. For those of you who’ve had some experience with surface modelling – you’ll know that this isn’t always easy!
The T-Splines subdivision surface technology in the Freeform toolset make it easy to create completely smooth, curvature continuous, ‘Watertight’ Nurbs surface models, that you can convert to ‘Brep’ (Solid) models for use with Inventors traditional solid modelling tools.
Where does subdivision come in?
Subdivision is usually a term that you’d hear applied to Poly-mesh modellers like Modo or Maya. Subdivision is a mathematical algorithm applied to a surface mesh to add complexity to a mesh to make it look smoother.
The clever bit about SubD modelling in T-splines is that you can subdivide individual faces, so that you only need to add complexity to your surface where you want additional detail.
You can see T-Splines subdividing faces in this excerpt from my Video tutorial series ‘Mastering Inventor T-splines‘.
The ability to add more control points and more control splines in a limited area is really helpful in allow us to add detail, without adding mathematical complexity to the surface.
This really helps Inventor to process the T-Splines surface quickly when we want to convert our Freeform model back into a Brep solid.
How is Freeform different other Inventor tools?
Freeform in Inventor 2015 is actually a completely separate modelling environment. Freeform surface models are edited using direct manipulation. They are not parametric and there is no History (Apart from the UNDO tool!).
How is Freeform different to T-Splines in Rhino or Fusion 360?
The Freeform toolset in Inventor 2015 is the very first implementation of T-Splines inside inventor, so not all the tools from the original Rhino version have been ported over yet. What you get in Inventor 2015 is the most basic set of tools that make Freeform modelling practical.
One big difference is how the Inventor implementation handles conversion to Brep’s. Instead of converting to a Brep on command, Inventor constantly calculates the T-splines surface in the background. This means that the Brep model is instantly available as soon as you leave the Freeform environment.
The constant checking of the Brep surface means that Inventor can give you some pretty good feedback on your T-Splines surface as you work on it. If your operation will cause the Brep to fail, Inventor will warn you.
The slight downside to this is that the constant checking is compute intensive, and might mean that you need a more powerful computer to make best use of T-Splines.
So when WOULD I use the Freeform tools?
The Freeform tools are really helpful when you want to throw down an organic surface without having to spend lot of time planning and executing individual surface patches. T-spline surfaces are simple and intuitive and it’s really easy to iterate through a number of different options.
So when WOULDN’T I use Freeform?
The Freeform tools are great for styling designs. If you are in Industrial Design or Product Design, you are going to find these tools really helpful. Freeform T-Splines surfaces are not going to help with precisely engineered designs for items such as propellers or mechanical screws.
How can I find out more about Autodesk Inventor 2015’s Freeform T-spline tools?
Click this link to find out more about my Video training series ‘Mastering Inventor T-Splines’ from Infiniteskills.com