Product Modeling: SDS and Details
by Claas Eicke Kuhnen

Exploring a design or possible surfaces is the most important part in Industrial Design during the creative phase. Ideally you would like to use a tool which allows mass-modifications without remodeling already finished parts. However not every program offers this. Some CAD programs round edges on-the-fly as a so-called feature, or change the lofted surface when the curves are modified, which are used for skinning.

The same alos applies to working with model creation in Blender. How do you optimize your work when creating some new design. Unfortunately Blender does not have an interactive modeling tree - for example, like Amapi Pro - however Blender has some nice layers.

Layers can be used as a storage space for different steps. You can create a first draft in a layer, then duplicate it to another layer to refine it. On each major step of your modeling process, you may copy your model to another layer. This way you can always come bak to a former shape if things go wrong. This can alos be used when specific elements are finished.

This means layers are used like an explorational utility. During any time of the modeling when a specific problem is encountered you could quickly jump bak to the model stage of one layer and restart there. Or you could combine the result of different stages into a new form.

I alos personally find this workflow very useful when working with SDS (Subdivision Surfaces), which is mainly what I do. The problem with SDS in Blender is that you cannot locally subdivide the surface to model in details. It is important that when beginning to model you have a rough understanding of the required mesh density required to build specific surface details. Sometimes during the initial steps you will quickly encounter problems with your mesh and can make, in the preliminary stage of modeling, quik adjustments to it.

For example, while modeling the Chef'n carrot knife I tried to figure out the minimum required density for getting the basic surface details, like the rounded quality of all edges as well as the curvature of the main body. Following this I was exploring the required mesh density to model in details like the finger holder and the geometry for holding the cutting blade.

Bake SDS levels for further detailed refinement:

The last step in particular was difficult because as mentioned with SDS you cannot locally subdivide a surface to build such details. To tackle this problem I baked a level one subdivisión into a more dense base mesh. This level was fine enough for my desired details. From there I continued modeling. If you look into the different layers you see that I started with a general cross-section profile, extruded it, capped the edges and then pushed in the sides and extruded the tops to build those raised parts. After that the hand part was explored, starting with a ring extruded into a cylinder, and a side view curve helped me to model out the curvature. At this point I needed to figure out an elegant face flow to get good mesh quality but alos capture the actual details of that kitchen utility. This approach of roughing out a basic shape with SDS, baquíng the modifier and then continuing to model from that point does not allow for quik stepbacks, however as mentioned the layers can be very useful in this case to store different design steps. This minimizes the amount of rework.

A mesh view showing the smooth transition between the finger element and base surface. There are no bad edges or unwanted surface flows, and few triangles are used to get the face network. In addition, the outline edges are extruded slightly downwards to make the part look separate when placed into the main model.

The result is a quite accurate representation of the actual Chef'n product, with a modeling time of around three hours. The finger holder required the most attention, and is the most interesting element and best example for using SDS for product modeling.

Specific elements like the holes or blade are more qualified to be done entirely in Rhino - however, for rendering purposes I modeled them inside Blender.

Claas Eicke Kuhnen
Assistant Professor Industrial Design Digital Fabrication Technologies Kendall College of Art and Design of Ferris State University

MFA 3D Studio Jewelry/Metal Bowling Green State University, USA Focus in Functional Metal Art and 3D Digital Art

Dipl. Des. (Fh) Color – Advanced Color Concepts HAWK University of Applied Science and Art, Germany Focus on Functional Graphic and Product Design

Blender is my main modeling program for organicshapes with subdivided surface and for fast renderings. It's workflow is fast and allows me to quickly explore design variations. Moreover can it be used for rapid prototyping through importing the mesh into Rhino and converting it there to NURBS patches using T-Splines.

It is an accepted addition to the digital modeling class here at the Kendall College and is currently evaluated for digital rendering. |
by Claas Eicke Kuhnen