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December 1, 2013

Polygon Reduction with Meshlab

There's a limit to the complexity of objects that you can upload to Shapeways: they can have no more than 1 million polygons. More polygons than that quickly become too much work for our servers and printers to handle.

Some tools like ZBrush can quickly create a high polycount, so its easy to run into this limit. Fortunately there's a solution known as polygon reduction (also known as mesh decimation). Chances are that your 3D application already has this built-in, otherwise the open source tool MeshLab offers an excellent alternative. MeshLab is available for Windows, OSX and Linux.
The picture below shows the results of a test I did with a small toy car model that had 480,000 faces. Down to 120,000 faces, the difference in quality is hardly noticeable. Below that, you'll see the model becoming rougher and rougher (click on the image to see the high-res version):

Let's get started!

If you haven't already done so, please download and install MeshLab and import your model.
From the menu, select Filters > Remeshing, simplification and construction > Quadratic Edge Collapse Detection. If your model is textured, there is also an option (with texture) that will do a good job at keeping your textures positioned properly. A panel with a few options will show up. You can click on the 'Help' button to get extra information about the available options, but that didn't answer all my questions so I checked with the creator of MeshLab, Peolo Cignoni.
Here are the option settings we believe to be optimal:
Target number of faces - Self explanatory
Quality threshold: 1. Enter a value between 0 and 1 here; the higher the value the harder MeshLab tries to stick to your original model's shape. The documentation isn't clear on what the consequence of using a higher value is - my impression is that it's slightly slower than low values, so I happily used a value of 1 with great results.
Paolo's comment: 'Quality threshold affects the simplification penalizing bad shaped faces. To approximate accurately the original shape only with well shaped triangles you require a higher number of faces with respect to allowing more freedom in the final triangle shape. The value is in the range [0..1]: 0 accept any kind of face (no penalties), 0.5 penalize faces with quality < 0.5, proportionally to their shape".
Preserve Boundary of the Mesh: Yes. Paolo's comment: 'The simplification process tries not to destroy mesh boundaries, e.g. exposed edges of the mesh are left untouched. This parameter has no effect on watertight meshes.'
Preserve Normal: Yes. Select this to stop MeshLab from accidentally flipping the face normals. Paolo's comment: 'Try to avoid face flipping effects and try to preserve the original orientation of the surface. The only drawback of enabling it is a slight increase in the processing times. On by default.'
If you DO run into inverted normals issues when uploading, try reorienting the normals with the option Filter > Normals, Curvature and Orientation > Re-Orient all faces coherently (note that this will only work for manifold objects).
Optimal position of simplified vertices: Yes. Paolo's comment: 'When collapsing an edge the chosen vertex position minimizes the current estimated error. If disabled, the edges are collapsed onto one of the two vertices and the vertices of the final mesh are a subset of the original mesh. It’s on by default.'
Planar simplification: Yes. Paolo's comment: 'Add additional simplification constraints that try to preserve the current shape of the triangles. It can greatly improve the quality of the shape of the final triangles on perfectly planar portions of the mesh. Like the quality threshold it affects the accuracy/complexity ratio. Off by default because it is very useful only in particular situations like when you have perfectly flat areas finely tessellated.’'

3D-Printed Surfboards Are Custom Designed for Each Surfer

Madeboards1

Surfing pros and novices alike will be intrigued by an ongoing Kickstarter project from a company that wants to design 3D-printed custom boards based on actual data derived from riding in the water.
Chicago-based MADE Boards is trying to raise $450,000 on Kickstarter to further develop its sail, kite, surf, and paddle "SmartBoards." Using MADE's VOLUME mobile app for iOS and Android, customers can figure out what board is best for their own body and activity, and MADE will then custom build it.
MADEBoards3
MADEBoards2

Surfing pros and novices alike will be intrigued by an ongoing Kickstarter project from a company that wants to design 3D-printed custom boards based on actual data derived from riding in the water.
Chicago-based MADE Boards is trying to raise $450,000 on Kickstarter to further develop its sail, kite, surf, and paddle "SmartBoards." Using MADE's VOLUME mobile app for iOS and Android, customers can figure out what board is best for their own body and activity, and MADE will then custom build it.

The internal structure of the boards are 3D-printed, taking into account specific factors like shape, rigidity and how much the board curves. The board is then wrapped in bamboo underlayment and a fiberglass shell to stiffen it. MADE's founder Shanon Marks says additive manufacturing — or 3D-printing — lets the company factor in a person's geographic location, atmospheric conditions and the way the individual rides the board. Marks told Mashable their platform uses social data, performance tracking/journaling and big data to influence design.
"You look at a surfboard, you look at a sailboard and it has terabytes of data 'stored' inside of it," Marks said. "Like there's this amazing, amazing history of everything it does on the water. What if we could quantify that?" 

"Additive manufacturing really became the best way to do that because it's a direct translation from the data input that we're collecting."
Here's how MADE's process works for consumers: Download the performance-tracking VOLUME app (for Android and iOS) before you buy their equipment. Using any existing board you might have, put your phone in a waterproof case and wear it while you're riding it. Throughout various days, the app can collect insights on your performance that will be used as design influences for a new board. The app collects data like the time of day and year, but also cross-references with relevant atmospheric conditions: e.g., wind speed, wind direction, wave height, wave speed, wave direction, barometric pressure, altitude, and freshwater versus saltwater.
Using that collected atmospheric data, biometrics and aggregated social information from other VOLUME users, you'll get a suggested board that's meant to be just right for you.

MADEBoards4
Growing up windsurfing and sailing himself, Marks said MADE began out of the frustration that people pay thousands of dollars for equipment that he says isn't made for them.
"One of the unfortunate things that I witnessed in the (windsurf) industry is that there was a huge emphasis on specialization around materials and super high performance," he said. "The unfortunate part about it: That came at the expense of the consumer's wallet — like boards just got more and more and more expensive."
Marks hopes to make these sports more accessible. He also claims additive manufacturing is a win from an environmental standpoint, since 3D-printing can minimize material use.
MADE's Kickstarter campaign still has 18 days left to go and had only reached about one percent of its fundraising goal, as of Tuesday afternoon. Backers who pledge at least $799 can get a MADE kite board; $999 for a "series one" SmartBoard; $1,299 for a paddle board; and $1,499 for a sail board.
See one of Made's 3D-printed sailboards in action in this video:

Microstructure Model

Goldberg Polyhedron














George Hart’s model of Michael Goldberg’s polyhedron has quickly become the “Hello World” of resin printers. I tried to print a half of the model simply because it was in my test folder, not expecting it to print at all.  Surprisingly it came out reasonably well, except that the sides suffer from z-layer bleeding. Several of the holes remained filled with resin – some isopropyl alcohol and some diligent cleaning would sort that out I think. I should note that each square on the mat in the photos is 10mm across.

Failed Goldberg Polyhedron

Even the failed prints look good! Here the print failed to attach to the base and remained on the vat floor for the duration, leaving a 2D projection of the half-sphere.


Microstructure Model













This model is again from the Functional Representation program. In my search for efficient fill algorithms I came across the work of Alexander Pasko and various colleagues, particularly a paper entitled “Procedural Function-based Spatial Microstructures” (PDF) which details exactly what I was looking for. Since then I have been attempting to recreate their findings, particularly the models with parametrised internal structure. Last week I finally was able to create the model and so of course it was one of the first things I wanted to print. The photo’s do not really do it justice – and there is still a lot of improvements to make – but I was pretty excited to print some resemblence to the model. Below is an image from a later paper, “Procedural Function-based Modelling of Volumetric Microstructures” (PDF) which shows how the model should look. The first image in the gallery above is the model I created, and the photos are of a print of the middle quarter of the sphere, and some of the structure is clearly visible. I plan to write an entire post on this subject as I think there is a lot of potential in relation to 3D printing.


Volumetric Microstructure taken from "Procedural function-based modelling of volumetric microstructures", Alexander Pasko et al.

http://garyhodgson.com/reprap/category/dlp-resin-printer/

October 23, 2013

Open Ergonomics

Comfort

We have a particular specialty in seat comfort. Our comfort technology is in use by Air New Zealand, American Airlines, Delta, British Airways, Cathay Pacific, SAS, and United, and by Europe's largest railway seat manufacturer and the UK's largest bus seat manufacturer.
Most projects start with a definition of the occupants, for example using ticket sales data to find the proportion of different nationalities and the sex mix. This definition is used in PeopleSize to create an anthropometry database, from which the percentage of customers who will fit any particular seat dimension is determined. We also determine the proportion of occupants who will fit in every important dimension at once (some seats, when analysed like this, turn out not to fit anyone at all!).
Then we consider the opportunities in the specific situation for optimising the shape, adjustments, foam, and geometry of the seat. This stage takes into account the manufacturing technology, the space available, cost, weight and maintenance.
Testing can then include comfort trials, sleep trials, and pressure-mapping, and comparative testing can prove and quantify the advantage over the previous or competing seats..

Some Physiological Issues

The illustration below shows some of the factors that we deal with in seat design. The red arrows show the main gravitational forces on the body, and the green arrows show how the seat has to deliver its support.

sitskel.gif


The seat has to:
  • keep the correct curvature in the spine
  • stop the pelvis tilting backwards
  • minimise pressure under the coccyx (tail) and buttocks
  • manage high pressure under the pelvis (ischial tuberosities)
  • limit pressure under the hamstring muscles
  • provide good support under the pelvis and feet


To achieve this, the seat has to have an ergonomics specification, which includes dimensions, shape, geometry, adjustment ranges and cushioning.
Other factors can include head and shoulder posture, armrests, footrest, and movements associated with seated tasks.
Projects sometimes start with concept design using CAD modelling, to find the best postures within a given space. Sometimes the project is an Audit of an existing or prototype seat, looking for ways to make quick improvements.

http://www.openerg.com/seating.htm

October 17, 2013

Cushion Surface Modeling Based on Body Pressure Distribution and Subjective Rating

Paper Title: Cushion Surface Modeling Based on Body Pressure Distribution and Subjective Rating
Periodical
Applied Mechanics and Materials (Volumes 226 - 228)
Main Theme
Edited by
Chunliang Zhang and Paul P. Lin
Pages
2193-2197
DOI
10.4028/www.scientific.net/AMM.226-228.2193
Citation
Zhong Liang Yang et al., 2012, Applied Mechanics and Materials, 226-228, 2193
Online since
November, 2012
Authors
Keywords
Price
US$ 28,-

·         Abstract
This paper presents a method of ergonomic design based on subjective rating for the purpose of modeling cushion surface mapped by body pressure distribution (BPD) test data. A sitting comfort evaluation scale was designed to collect subjective comfort perception. Optimal BPD test data were selected by comparing comfort rating after experiments on a trial seat. A data mapping model was established between point clouds in three dimensional coordinate and BPD test data, which can be recognized and transferred in CAD system. In this context, an ergonomic-aided system was developed in practical application to demonstrate the viability of the method. Two designers tried out the system to design a seat cushion, and compared it with conventional method in Rhino software. Results show that the system is more interactive to designers, which can save time of surface modeling by about 50%.

Title:
Cushion Surface Modeling Based on Body Pressure Distribution and Subjective Rating
Author / Creator:
In:
APPLIED MECHANICS AND MATERIALS; 226/228; 2193-2197
Vibration, structural engineering and measurement; (ICVSEM 2012)
International conference; 2nd, Vibration, structural engineering and measurement; (ICVSEM 2012)
Publisher:
Trans Tech , Durnten-Zurich
Year of publication:
2012
Size:
5 Pages
ISBN:
ISSN:
Document type:
Conference paper
Type of Material:
Print
Language:
English
Keywords:
Vibration, Structural engineering, ICVSEM

Nissan Developing 'Fatigue-free' Seats For Future Models: Video


Nissan is developing a new seat design that aims to replicate the human body’s neutral posture, as experienced in a weightless environment.
Described as the ‘Comfortable seat with spinal support’, the design aims to emulate the posture the human body assumes under zero gravity.
While that's not a feeling many of us have experienced, NASA's astronauts have provided the data, and Nissan wants motorists to benefit from it.
According to Nissan, the neutral posture minimises loads on the body, reducing muscular activity, discomfort and fatigue through optimising blood flow.
In short, the new design promises to be more comfortable over longer periods than conventional seats.
“We devised a seat shape and cushion softness distribution that would closely reproduce such a neutral posture in a car seat”, Nissan’s Masahiro Egami said.
Intended for front and rear seating, the design uses a specific seat shape andtailored cushioning to spread pressure from pelvis to chest, where conventional designs concentrate pressure on the pelvic area.
The varying cushion softness distribution also promises to adapt to different physiques, with the obvious benefit of reduced whining from the back seat on family road trips.

Nissan hopes to equip all of its models with the technology in the future, but is yet to specify which particular model will see it first.




http://www.themotorreport.com.au/55304/nissan-developing-fatigue-free-seats-for-future-models-video

Ergonomic

https://www.google.co.kr/search?q=Ergonomic+diagram+of+car+and+driver&oq=Ergonomic+diagram+of+car+and+driver&aqs=chrome..69i57&sourceid=chrome&espv=210&es_sm=122&ie=UTF-8


https://www.google.co.kr/search?q=sammie&oq=sammie&aqs=chrome..69i57j0l5.2373j0j4&sourceid=chrome&espv=210&es_sm=122&ie=UTF-8#es_sm=122&espv=210&newwindow=1&q=automotive+ergonomics

SMMIE CAD

The SAMMIE system is a computer based Human Modelling tool. Its capabilities make it an invaluable tool to designers and design teams working on products that are used by people. The system offers the following advantages:
  • 3D analysis of fit, reach, vision and posture.
  • reduced timescale.
  • early input of ergonomics expertise.
  • rapid interactive design.
  • improved communication.
  • cost effective ergonomics.

http://www.lboro.ac.uk/microsites/lds/sammie/samdesc.htm

October 16, 2013

KRISS(한국표준과학연구원) 연구보고서

http://203.254.160.74/irisnetwebsearch/CxSitesKriss/SearchResultKrms.aspx?ddlCatalogOption=1&CallPageName=/irisnetwebsearch/CxSitesKriss/SearchFormKrmsCatOption.aspx&SearchKey=%20

Driver sitting comfort and discomfort (part II): Relationships with and prediction from interface pressure

  • Department of Industrial and Systems Engineering, 250 Durham Hall (0118), Virginia Tech, Blacksburg, VA 24061, USA

Abstract

Pressure at the driver–seat interface has been used as an objective method to assess seat design, yet existing evidence regarding its efficacy is mixed. The current study examined associations between three subjective ratings (overall, comfort, and discomfort) and 36 measures describing driver–seat interface pressure, and identified pressure level, contact area, and ratio (local to global) variables that could be effectively used to improve subjective responses. Each of 27 participants was involved in six separate driving sessions which included combinations of two seats (from vehicles ranked high and low on overall comfort), two vehicle classes (sedan and SUV), and two driving venues (lab-based and field). Several pressure variables were identified as more effective for assessing sitting comfort and discomfort across a range of individual statures. Based on the results, specific approaches are recommended to improve the sitting experience: (1) lower pressure ratios at the buttocks and higher pressure ratios at the upper and lower back; and (2) balanced pressure between the bilateral buttocks, and between the lower and upper body. Finally, separate analyses supported that human–seat interface pressure was more strongly related with overall and comfort ratings than with discomfort ratings.

Relevance to industry

Several interface pressure variables were identified that showed associations with subjective responses during sitting. Use of these measures is suggested to improve the quality of car seats.

Keywords

  • Interface pressure
  • Sitting comfort
  • Driving posture
  • Packaging