Aliasdesign.autodesk.com - Surf

8/4/2019 Aliasdesign.autodesk.com - Surf

1/4

SurfaceConstruction: Series Introduction

Posted February 17, 2009, 3:17 pm by , Barry Kimball

IntroductionMy name is Barry Kimball. I would like to layout out the foundations for a series of tutorials that will discuss some

theories of Surface construction. To begin I would like to inform you of where my theories originate. Over the past20 years I have been working in the field of automotive surface modeling. Those years have provided me the

opportunity to work with some very knowledgeable people from around the world. The surface construction

fundamentals that I will convey are not based on one companys standards, one persons ideas, or even from one

culture.

Here is my background (20 years in one paragraph is as short as I can make it)I began working at General

Motors building door inner and body side sheet metal. (A body side panel is the sheet metal structure the door

hinges mount on) That experience allowed me to work with exterior surface data from GMs Styling group and

eventually work in the Cadillac styling department. During that time I also realized the technical complexities of

exterior and interior surface development. I had the opportunity to learn many software tools for analyzing and

creating surface models. Over that time I became aware that I had a passion for developing software tools that

aided in class-A surface development. I moved from GM to Alias|wavefront. My time at Alias sent me to Italy,

German, England, and all over North America. Some trips would be for sales or training and some for

benchmarking against competitive products. From Alias, I moved to Ford Motor Co. and developed training

materials and mentored AutoStudio users in the creation of production and conceptual surface models. The last

18 months at Ford I spent working on the Ford GT production car in the Living Legends studio. Since then I have

worked At Nissan Design America as a digital designer creating some concept cars (Nissan Azeal) and many

production vehicles.

During this time I have made a few discoveries. I have found that the basis for surface construction is notdocumented somewhere in a book or with an organization like the S.A.E. Many people would even insist that

there are no fundamental rules, build what looks good. Contrary to that belief I would say that a community of

users has established a set of criteria that defines acceptable surface data from a technical and aesthetic

standpoint. This is not a list of tolerances, specific levels of continuity, degree of a surface, or even if the surface

is NURBS or Bezier. Highly qualified surface modelers would identify proper surface construction based on a very

short investigation of a 3D model, no matter what software was used to create the data.

Surface LayoutI would like to begin our discussion of surface theory with one of its fundamentals, surface layout. Here are some

basic guidelines for surface layout.

Surface Layout Guidelines:

- Attempt to base the surface layout on the shape of features

- Features should define areas of equal curvature

- Areas of equal curvature (Features) should be represented by a single surface

- Feature definition should include where features begin/end & merge

The following example shows a conventional surface layout extracted from STL data for a golf club head. The

basic guidelines previously described were used to layout where individual surfaces begin, end and merge.

Recommendto a Friend

You must sign in to share pages.

SubmitFeedback

You must sign in to send feedback.

Register | Sign In Tags | Search

Stories Tutor ia ls

Page 1 of 4AliasDesign :: Surface Construction: Series Introduction

8/28/2011http://aliasdesign.autodesk.com/learning/tutorials/details/Surface%20Construction:%20Ser...


2/4

Some users might suggest trying and develop such an organic shape using one surface, or only a few. This

method may work and achieve the same end result. The surface community will not consider the modeltechnically correct. The technically correct methods may seem picky or too time-consuming to many users. Over

the next few tutorials we will discuss the methods used for the surface boundary construction for the surface

model and why it is important to lay out surfaces correctly.

This is another example of surface layout that indicates various users could define a set of surfaces.

The left and right multi-colored surfaces show two different surface layouts. The center is a sky-textured

polygonal mesh the structures are based on...

The structure on the left has more surfaces. This means that the users must control more boundary continuity

conditions. The surface layout on the right has fewer surfaces that are more complex individually.

I would recommend looking back to the original guidelines, dont attempt to do too much with one surface. Thisexample shows that a surface modeler can change the design/shape of a part. Notice the differences between

the left, middle, and right ears. The right hand models ears are much pointier than the scan. Highly complex

NURBS surfaces can also be more difficult to modify and enhance.

While neither of these models would be considered class-A the left model is more technically correct in many

ways. I will show ways to identify surface to scan deviations and diagnose surface models over the next few

tutorials.

Pay attention to where features begin, flow, and end. This example shows the differences between two users

interpretations of surface layouts extracted from scanned sections.




3/4

The left example indicates a blend that flows from left to right. The right example indicates a blend that stops and

starts in an area divided by another feature (an air intake). Neither example is specifically correct. When possible

consult the designer to capture the correct flow of each feature. If the design is yours feel free to define the

shapes that are most pleasing to you. Based on experience I would say the left model is correct.

I will discuss how to identify where features begin and end over the next few months.

Theoretical intersections are extremely important to surface structure. Here are two examples that show how

theoretical intersections can influence the shape of a model.

The top example has a fully defined theoretical, the bottom has a partially defined theoretical. (As shown by the

exposed CVs and Hulls) By a partially defined theoretical I mean to say that the wall surfaces do not meet at the

theoretical along its entire length. This may allow the fillet to bias itself to one side or the other of the part. This

can cause the highlights to sag or constrict in areas that should flow or be consistent.

Over the next few months, we'll delve into greater detail. In the next few tutorials, we will look for methods to

analyze surface shape.

-Barry

DownloadableFiles

There are no Downloadable Files.

Copyright 2008 Autodesk, Inc. All Rights Reserved. Legal Notices & Trademarks Privacy Policy




4/4


8/28/2011http://aliasdesign autodesk com/learning/tutorials/details/Surface%20Construction:%20Ser

Aliasdesign.autodesk.com - Surf

Documents

Transcript of Aliasdesign.autodesk.com - Surf