Quantifying Design: The Geometric Properties Behind Designer Choices and Human Perception

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               ***Joint Seminar***
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The Hong Kong University of Science & Technology

Department of Computer Science and Engineering
Center of Visual Computing and Image Science
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Speaker:        Professor Alla Sheffer
                Computer Science Department
                University of British Columbia, Canada

Title:          "Quantifying Design: The Geometric Properties Behind
                Designer Choices and Human Perception"

Date:           Thursday, 18 April 2013

Time:           2:00pm - 3:00pm

Venue:          Lecture Theater E, HKUST

Abstract:

Over centuries artists and designers had developed effective tools to
communicate notions of shape to the general public. Even coarse artistic
sketches are surprisingly effective at unambiguously conveying complex 3D
shapes.  While artistic guidelines provide many useful hints as to how to
describe shape effectively, very little is known as to why these tools are
effective and what geometric properties of the described shapes they
capture.

Our work combines artistic guidelines and insights from perception
literature to introduce an explicit mathematical formulation of the
relationships between the communication tools used by artists and the
geometric properties they aim to convey.  In this talk I'll discuss the
application of the developed mathematical formalism to two challenging
computer graphics problems: shading of concept sketches and surfacing of
artist designed 3D wireframe models.

The first framework facilitates the creation of 3D-looking shaded
production drawings from concept sketches. The key to our approach is a
class of commonly used construction curves known as cross-sections that
function as an aid to both sketch creation and viewer understanding of the
depicted 3D shape. In particular, intersections of these curves, or
cross-hairs, convey valuable 3D information, that viewers compose into a
mental model of the overall sketch. We use these artist-drawn
cross-sections to automatically infer the 3D normal across the sketch,
enabling believable 3D-like rendering. We validate our formulation and
algorithm through a user study and a ground truth normal comparison.

The second problem I'll briefly address is surfacing, and specifically
quadrangulation of closed 3D curves created by artists via sketch-based or
other curve modeling systems. We use the input curves to both conceive and
construct the quad-mesh of an artist imagined surface bounded by them. We
observe that viewers complete the intended shape by envisioning a dense
network of smooth, gradually changing, flow-lines that interpolates the
input curves. Our algorithm mimics this behavior and interpolates the
input curves by a network of quadrilateral cycles whose iso-lines define
the desired flow line network.

More information is available at:
http://www.crossshade.com/
http://www.cs.ubc.ca/nest/imager/tr/2012/Quadrangulation/


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Biography:

Alla Sheffer is an associate professor in the Computer Science department
at the University of British Columbia. She investigates algorithms for
geometry processing focusing on computer graphics applications. She is
particularly interested in geometric interpretation of designer intent
when conveying shape. Alla regularly publishes at venues such as Siggraph,
Siggraph Asia, Eurographics, and the Symposium on Geometry Processing.
She is the recipient of the Symposium on Geometry Processing. She is the
recipient of an NSERC DAS (2012), an Audi Production Award (2011), a
Killam Research Fellowship (2009), and an IBM Faculty Award (2006).