Aug 2, 2017 | By Benedict

Alla Sheffer, a computer scientist at Canada’s University of British Columbia, has developed software called “FlowRep” that can extract the “descriptive compact 3D curve networks” from manmade 3D shapes and use them to create visually informative 2D sketches.

There are many ways that we can discern the shape of a physical 3D object: we can turn it over in our hands, look at it from different angles, or even observe where shadows fall across its surface. But when we try to recreate a 3D shape as a 2D sketch, things can get a little bit muddled.

Think about it this way: how would you go about drawing a soccer ball in 2D without it looking like a flat circle? You can’t use shading, and you can’t draw shadows. For those of us who aren’t specialists in these matters, it’s something of a head-scratcher.

Alla Sheffer, a computer science professor at the University of British Columbia in Canada, has designed a program called FlowRep that aims to determine the key bits of information from a 3D object that allow us to understand its shape.

It can do this by identifying and extracting “descriptive compact 3D curve networks,” imperceptible lines that map out the 3D shape of an object.

“If you try to explain what your computer mouse looks like to someone who has never seen a mouse before, you’re going to struggle to verbally describe its shape,” Sheffer explains. “Humans are good at verbally describing color or dimensions, but cannot easily articulate geometric properties. The easiest way to describe shapes is to sketch them.”

But identifying the lines that will accurately depict a 3D object (in 2D!) is harder than you think. It’s something that artists are good at, but making a computer identify and generate these lines presented a big challenge for Sheffer and her team.

FlowRep was recently demonstrated at SIGGRAPH 2017, the world’s largest computer graphics and interactive techniques conference. To make the program, Sheffer used insights from Gestalt psychology, a movement in psychology from the early 20th century that explains how humans interpret visual content and understand depth from 2D drawings.

These insights informed a set of clever algorithms that can turn all sorts of complex 3D shapes into simple yet fully descriptive sketches.

“All you need is a dozen strokes or less and people will be able to envision the geometry of an object,” Sheffer said. “This program answers the question about which surface curves we need to trace so that human observers can imagine a shape.”

Sheffer and colleagues had previously used a similar line of thinking to develop algorithms that turn sketches into 3D shapes—the opposite of what they’re doing now. Interestingly, both kinds of algorithm could be used to improve 3D printing, allowing users to quickly generate 3D printable objects from 2D sketches or turn 3D printable files into visually recognizable 2D blueprints.

FlowRep reportedly performed well in user studies, with the automatically generated sketches deemed comparable to those made by professional designers.

There’s more to be done on the software too. Future research on the project could see FlowRep adapted to sketch organic 3D shapes as well as manmade ones.

The study was carried out in cooperation with Adobe Research and Washington University in St. Louis.

 

 

Posted in 3D Software

 

 

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