NOVEDGE blog

Interview with Matthew Sederberg, CEO and Founder of T-Splines

One of my recurring complaints about surface modeling is the intrinsic complexity of existing modeling systems. Even if the level of user friendliness of these systems has improved, sooner or later every user needs to invest some time to understand how the underlying geometry works and to accept the limitations that come with each modeling strategy. T-Splines are certainly one of the most important innovations in this field, but mostly important, the technological benefits of the T-Splines geometry make life easier for the user and the modeling activities faster and more enjoyable. The recent release of T-Splines 2.0 for Rhino shows the huge potential of this new technology. On top of this, T-Splines are fully compatible with existing NURBS modeling systems such as Rhino and Maya. Let's have Matthew Sederberg (blog), the son of the T-Splines inventor and CEO of the T-Splines company (website), help us to understand better what I like to call NURBS 2.0.

Matt can you tell us a bit about yourself and your professional activities?

[T-Splines] has received funding from the US Navy for its work in innovative surface modeling technologies

Hi Franco, and thanks for the interview. I started T-Splines, Inc. while still in college at Brigham Young University (Provo, UT) in 2004. The company hatched slowly for the first couple of years as our founding team graduated, but we've been growing strong ever since our first commercial industrial design product release in 2007. T-Splines has been the recipient of an NSF SBIR grant, a Utah Center of Excellence grant and has received funding from the US Navy for its work in innovative surface modeling technologies. The company is based in Provo, Utah where I also live with my wife. When I'm not working, I enjoy playing tennis with my wife.

T-Splines is not only a company, it's also a new way to handle a surface's geometry. Can you tell us when it was invented, by whom, and how it became a product?

The T-Splines technology was introduced in 2003 by Dr. Tom Sederberg, my dad

The T-Splines technology was introduced as a SIGGRAPH paper in 2003 by Dr. Tom Sederberg (my dad). Previous to inventing T-Splines, he had spent his career doing research in computer graphics, including inventing free-form deformation and doing extensive research with NURBS. We were very excited about the potential of T-Splines to significantly improve design processes, and since the CAD industry is usually slow to adopt academic research into commercial products, my dad and I decided to commercialize the T-Splines technology ourselves. For an even more focused commercialization, instead of writing an entire program, we wrote plugins: our first product, a plugin for Maya, was released in 2005, and T-Splines for Rhino was released in 2007. T-Splines 2.0 for Rhino was released in May 2009 and is a very significant enhancement.

What are the benefits of using the T-Splines system compared to using a standard NURBS modeling system? Are there any disadvantages?

a large percentage of NURBS control points are superfluous

NURBS are the basis for almost every commercial CAD software on the market today. However, NURBS do have several limitations as compared to T-Splines:

1. A non-uniform rational b-spline Surface or NURBS surface is defined by a set of control points which lie, topologically, in a rectangular grid. This means that, in practice, a large percentage of NURBS control points are superfluous in that they contain no significant geometric information, but merely are needed to satisfy the topological constraint. In a typical complex surface model, 40-50% of the NURBS control points are superfluous. In contrast, a T-Spline’s control grid is allowed to have partial rows of control points. A partial row of control points terminates in a T-Point, hence the name T-Splines. Minimizing control points makes it easier to create models, control surface smoothness, and speed up editing time.
2. As a direct result of the ability to create partial rows of control points within a single surface, the user can now create a surface with varying level of detail only where required. Refinement, the process of adding new control points to a control mesh without changing the surface, is an important basic operation used by designers. A limitation of NURBS is that refinement requires the insertion of an entire row of control points, increasing the density of the mesh across the entire surface. T-Points enable T-Splines to be locally refineable. Support for local detail in a single surface makes it easier to model complex shapes and create smooth watertight models.
3. With T-Splines, non-rectangular surfaces can be constructed using star points, also called poles or extraordinary points. This overcomes another fundamental NURBS limitation: In NURBS surface modeling, constructing a complex shape with varying detail, curvature or smoothness requires many individual rectangular patches. Maintaining continuity and smoothness across these patch surfaces is a significant challenge. Star points also enable modeling techniques such as extrusion, face deletion, and merging of surfaces that greatly increase design freedom for the user. Star points are used today in subdivision surface modeling, which is popular in animation, but T-Splines introduces them to industrial design in a NURBS-compatible format for the first time.

star points enable modeling techniques [...] that greatly increase design freedom for the user

As far as disadvantages for T-Splines, there are definitely some operations (such as exact fillets) where I would recommend NURBS over T-Splines. Also, where your design is primarily a prismatic part with mostly planar or cylindrical surfaces, a standard NURBS modeler is a better option. Today, T-Splines is an excellent choice for organic free-form designs and they are a great complement to existing NURBS modeling techniques. In the future, we expect to overcome the remaining limitations and T-Splines will have the potential to completely replace NURBS in modeling applications.

Based on your experience who are the users who can benefit the most from T-Splines?

our customers are industrial designers, architects, and jewelry designers

Most of our customers today are industrial designers, architects, and jewelry designers. T-Splines is also used in marine design and toy design. The sweet spot for T-Splines is for modeling organic designs, where the designer would like explore shape variations by pushing and pulling on the surface, and where staying compatible with NURBS for downstream applications or manufacturing is required.

In my opinion surface modelers have always suffered from an intrinsic complexity -- that of exposing too much of the underlying data structure and algorithms. How close are we to a truly user-friendly surface modeling system?

we've created a simpler interface by allowing users to select faces and edges and move them around

Great question. The benefit of surface modelers is that they give a high level of control over the surface being created, and this control often conflicts with simplicity. With the just-released T-Splines 2.0 for Rhino, we've created a simpler interface by allowing users to select faces and edges and move them around, Sketch-up style. We also let the user toggle on and off precision tools such as tangency handles, and have introduced a manipulator that can be used to intuitively rotate, scale, and move objects.

You choose to offer T-Splines as a plug-in for existing modeling systems rather than creating your own standalone application. What convinced you to go for this option?

converting any T-Spline to NURBS is a push-button operation, as is converting any untrimmed NURBS to T-Splines

The T-Splines technology is not the first alternative surface technology to be invented; however, T-Splines stands apart in its compatibility with NURBS. Converting any T-Spline to NURBS surfaces is a push-button operation, as is converting any untrimmed NURBS to T-Splines. Consequently, we decided to lower the barrier for designers to use T-Splines in conjunction with NURBS by placing T-Splines right into NURBS modelers. This also allows us to focus our resources on developing unique T-splines functions instead of rewriting NURBS routines.

I would like to thank Matt for taking the time to answer my questions. If you have any questions for Matt or for Novedge, please leave a comment below and we will be glad to answer.

Franco Folini

Why Direct/Parametric Modeling Hybrid is an Oxymoron

Parametric CAD systems are based on a complex internal data-structure that represents each geometrical and dimensional constraint as a relationship among two or more entities. When the end-user requests a change to a parameter (dimension), the CAD system propagates the modification to the entire 3D model (it’s called model evaluation) following those relationships while preserving the validity of each single constraint.

In the data structure of a direct-modeling CAD system there are no constraints. They are created on the fly as a way to support high-level modification of the 3D model. For example, if the CAD system sees a tangency between a planar face and a cylindrical face it likely will assume that it’s a constraint and that it should be preserved to guarantee that the behavior of the system follows the original design intent.

The power and beauty of the direct-modeling approach is that in different moments the set of active constraints can change radically. Constraints “captured” to support modification "A" can even contradict constraints “captured” during modification “B”. This is great because gives the end-user incredible flexibility and power.

On the other hand, in a parametric CAD system the set of constraints can be changed only with tedious and complex operations. The benefit of this more rigid approach is that your CAD system knows all the constraints and doesn’t have to guess them. This makes parametric CAD systems more predictable and reliables. If the 3D parametric model was carefully created by a skilled CAD user this can be a huge advantage.

Because of the intrinsic difference between the two approaches, there cannot be a hybrid CAD system where I can create a parametric part, change it using some of the flexible tools offered by a direct-modeling system, and still have a fully parametric part.  A direct-editing modification to a parametric model is possible, but it becomes a non-return point -- the data structure that supports the parametric nature of the model will not survive.

The recent marketing brochures and blogs that are describing a possible future of CAD based on the hybrid approach make me smile. But we all know that marketing knows no limitations…

Franco Folini

An Interview with Giuseppe Bocchi, Engine Designer

Giuseppe Bocchi, Founder and CEO of BRD srl, is a top-notch Italian mechanical engineer with a passion for mechanical engines (internal combustion engines). He has an incredible breadth of experience built working for prestigious companies such as Lamborghini, Ferrari, Ducati and MV Agusta, where as Chief Project and R&D Engineer he designed and brought to world dominance the four cylinder St. 76/50 and St. 76/35 racers led to World Title supremacy by Giacomo Agostini and Phil Read.

I met Giuseppe Bocchi several years ago in Parma (Italy) when he was still using the drawing board for the early stages of the design process.  At that time I was working for the University of Parma and with my students we were looking for some real-world exercises. I asked Giuseppe for the design of an engine part to optimize its shape with the use of software tools. He gave us a 2D handmade technical drawing of a new engine he never had the time to complete. We went back to the lab. The students created a full 3D CAD model of the selected piece. We noticed an unusual group of ribs across the part. At first glance, they looked excessively sized to us, and we asked Giuseppe the reason. His simple answer was: "At this stage of the design process I don't have any data, but the part looks beautiful with those ribs." We went back to the lab and the students ran several tests with a sophisticated FEM/FEA tool trying several 3D models with differently sized ribs. All the results pointed in the same direction: the best possible ribs were the ones chosen by Giuseppe. That day I learned that the greatest designers need FEM/FEA tools only to produce the final technical reports; they intuitively recognize the optimal shape simply as the most beautiful. Giuseppe Bocchi is one of these exceptional designers.

Giuseppe, can you tell us a bit about yourself and your professional activities?

I started working for very famous and world renowned companies such as Lamborghini, Ferrari, MV Agusta, and Ducati

I’m the President of BRD, a company active in the field of highly advanced design of hi-tech internal combustion engines. Our primary activity is the development of “turn key” projects (from basic calculations to CAD-CAM & CAE production blueprints) of highly advanced internal combustion engines.
After graduating from the University of Bologna, I started working for very famous and world renowned companies such as Lamborghini Automobili, Ferrari Automobili, Pederzani Automobili Racing Team, and MV Agusta, Ducati.
In 1980 I started my own design and research center: BRD. I still lead in my company as both President and CEO and as highly inspired scientific and technical leader of the design and engineering teams. Through the past 24 years of its activity, BRD has been offered the opportunity to cooperate with some of today’s leading automotive and motorcycling companies. For these clients we have developed projects of engines for both racing and street use. In addition to that, we have been very successfully operating in aerospace engineering, and specifically in the development of kerosene fueled turbo-diesel engines for light and medium aircrafts and drones.
The advanced activity specifically concerning modeling, simulation, and experimental validation of acoustics and thermo-fluidodynamic phenomena in internal combustion engine is fully executed in house thanks to dedicated softwares developed and patented by BRD. BRD also supports a full loop R&D and design activity with its capability of developing, manufacturing and fully testing the related prototypes within its state of the art facilities.
I'm also the author of a book “Motori a quattro tempi” (Four Stroke Engines), sold in many thousands copies, published by Hoepli, the most important scientific publishers in Italy.

You started designing long before the appearance of CAD systems for the PC. Which CAD systems are you currently using and how are you using them?

We currently use Pro/Engineer, Unigraphics, SolidWorks, and AutoCAD. In my experience Pro/Engineer and Unigraphics are the best tools for designing engines. Pro/Engineer is more specific for mechanical engineering of internal combustion engine, but it’s more rigid than the others. It’s widely used in Europe. I believe a very popular CAD system in US is the very powerful and complete Unigraphics. It has several modules and it supports the design of the whole vehicle. Also CATIA has this capability, but it’s more used in the aerospace industry. I consider SolidWorks the easiest, but I found it limited in the management of assemblies and complex surfaces.

As a consultant you have been working with manufacturing companies all over the world. How have your clients’ requests changed over the years?

the tendency today is to have a complete and ready project including the prototype

The complex mechanism of business changes day by day. The tendency today is to have a complete and ready project including the prototype. Some years ago our activity was mainly consultancy and engine design. Today customers, especially those of Europe, want a running prototype and they put in the contracts requests for warranties and penalties.
It is important to assemble and test the prototypes in our facilities, because as the designers of the engine and we know very well the characteristics of the product. So we can easily find the best tuning.
For this reason, we have a workshop and a test bench located near the technical office.

You are very active with emerging manufacturing companies from China. So far how has your experience been working with them?

now BRD is well known all over the world

It started more or less two years ago. The contact happened quickly and spontaneously. Usually Chinese manufacturers send scouters to Europe to study the European companies. Then the chairman comes to visit the chosen ones and at the end they draw up the contract. Chinese people don’t want to be contacted, they prefer to start the contact themselves. In fact, three years ago, we tried to approach some Asian companies with an Internet advertisements campaign, but with no result. Now BRD is well known all over the world.
Chinese people are very detail-oriented, unlike Italians, and with them it is difficult to reach agreements in a short time. They can work without breaks for many hours. They have a different concept of work. Initially communication is difficult; after a while it becomes much easier.

You have a long history of designing internal combustion engines. What are the strengths and the limitations of CAD systems in supporting these designing activities?

we have to buy several CAD systems to satisfy different customers' requests

Of course CAD technology allows designers to save time and money. During the design process, a designer with a CAD system can make a modification easily and quickly. With the old drawing board we had just two dimensions: thanks to CAD today we can work with three dimensions and so immediately have the a full perception of the model. Moreover, during the design process, CAD also allows for the control of the movements of all parts of the engine design: the dimensions, the drafts, the tools paths and the layout in general. It simplifies the designing of the production cycle, from the casting to the final tooling. Usually an interface is available between the CAD system and rapid prototyping and rapid tooling, so the prototyping and production times are short. Another very important capability is the integration between CAD and CAE systems. It’s possible to make simulations to optimize the shape and the structure of some critical parts. For example, through fluidodynamic simulation it is possible to optimize the shape and the geometry of manifold and mufflers; with aerodynamic simulation it’s easier to design a correct shape for the bodies. So the modifications can be made without the construction of the real parts.
In spite of that, we have to buy several kinds of CAD systems, because we have to satisfy different customers' requests: everyone use a particular CAD. To create an efficient designing department is expensive because it’s necessary to buy several licenses (one for each working station), to pay the training courses, and to stay updated with the last release of the software. And this kind of software needs an adequate hardware infrastructure.
On top of that, there are some bugs in the CAD code, so sometimes it can be difficult working with imported geometries.

I know you have been working on what might be revolutionary engine for some time. Can you tell us more about it?

this type of engine (cam engine) is very advantageous from the point of view of the thermodynamic efficiency

I think you are talking about “cam engine” (2 cylinders, 4 cylinders). This type of engine is very advantageous from the point of view of the thermodynamic efficiency. It takes advantage of the exploitation of the burnt gas energy, utilizing appropriate piston motion laws, different from the classical mechanism of the con-rod and crank.
Cam engines are very light, they have little axial dimension, and they are made of few components. For all these reasons and because of their low specific consumption, they are very suitable to the aeronautical applications.
I hope that in a near future this kind of engine will reach the production stage and attract some real customers.
The problem is to find the economical means to carry out the durability tests, to tune the engines under the pollution limits, and to start production.

Italy has an incredible tradition of designing the most powerful and beautiful cars (Ferrari, Lamborghini, Maserati, etc.) and motorbikes (Ducati, Guzzi, Cagiva, Aprilia, etc.). What is the status of the Italian mechanical industry?

fantasy and genius have always been characteristics of Italians

Fantasy and genius have always been characteristics of Italians. I think our realizations will always be unique, especially for high level products such as the ones you mentioned. Italian companies will always survive because their products are not repeatable and undergo continuous improvement. On the other hand, products at lower levels will be easy imitated and companies in this area will be overtaken from Asian markets because of their lower prices.
I foresee, in a near future, a very hard competition in this last field, made even harder as a consequence of the Italians' high production costs. This will be the most important problem for our politicians to resolve.

I would like to thank Giuseppe Bocchi for taking the time to answer my questions. If you have any questions for Giuseppe or for Novedge, please leave a comment below and we will be glad to answer.

Franco Folini

Update: I forgot to mention that in 1994 I wrote a scientific paper in collaboration with Giuseppe Bocchi. The article was presented at the 27^th International Symposium on Automotive Technology and Automation in Aachen, Germany and published for the ISATA proceedings. The title of the article is: Rapid Prototyping and Parametric CAD Systems.