Computer Graphics

Computer Graphics is about digital models for threedimensional geometric objects as well as images. These shapes and images may represent approximations of the real world or could be synthetic, i.e., exist only in the computer. Goals of computer graphics research are the generation of plausible and informative images, and computation with reasonable resources, i.e. in a short amount of time with little storage requirements. The models and algorithms for this task combine knowledge from different areas of mathematics and computer science.

NPAR 2015: The Markov Pen – Online Synthesis of Freehand Drawing Styles


Learning expressive curve styles from example is crucial for interactive or computer-based narrative illustrations. We propose a method for online synthesis of free-hand drawing styles along arbitrary base paths by means of an autoregressive Markov Model. Choice on further curve progression is made while drawing, by sampling from a series of previously learned feature distributions subject to local curvature. The algorithm requires no user adjustable parameters other than one short example style. It may be used as a custom “random brush” designer in any task that requires rapid placement of a large number of detail-rich shapes that are tedious to create manually.


See the project page for more details.

Eurographics 2015: Approximating Free-form Geometry with Height Fields for Manufacturing


We consider the problem of manufacturing free-form geometry with classical manufacturing techniques, such as mold casting or 3-axis milling. We determine a set of constraints that are necessary for manufacturability and then decompose and, if necessary, deform the shape to satisfy the constraints per segment. We show that many objects can be generated from a small number of (mold-)pieces if some deformation is acceptable. We provide examples of actual molds and the resulting manufactured objects.

See the project page for more details.

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Panono one of the 36 coolest gadgets of 2014

Panono-Panoramic-Ball-Camera-5Panono’s panoramic camera, originally developed as a thesis work by CG alumnus Jonas Pfeil is now in it’s second revision and has been selected one of the 36 coolest gadgets in 2014 by CNN.

Eurographics Outstanding Technical Contributions Award


Prof. Alexa receives the Outstanding Technical Contributions Award of Eurographics. The award is “given each year to an individual in computer graphics to highlight some outstanding technical achievement.”

The award has been presented at the yearly main conference of Eurographics, which took place in Strasbourg, France this year.

Andy Nealen’s Osmos on The Simpsons!

Screen Shot 2014-04-15 at 9.51.34 AM

Prominently featured in an episode of The Simpson was CG alumnus Andy Nealen’s game, Osmos: Milhouse had his iPad stolen on “The Simpsons.” When he finds it in Bart’s possession and begins to confront him, he is entranced by “the music of this bubble game.”

Panono at TV Total


Jonas Pfeil, alumnus of the CG group, is turning his thesis work into a product: panono – a panoramic ball camera. Right now they are running a crowd-funding campaign on indiegogo and he appeared at TV Total, a popular late night talk show.

Avoiding inbreeding in science and art

Prof. Alexa has been elected to the executive board of the Hybrid Plattform. He had been active in trans-disciplinary projects for years, strongly believing that this keeps science and research well-grounded.

SIGGRAPH Papers Chair

alexaProf. Alexa had been elected to chair the technical program of SIGGRAPH 2013. SIGGRAPH regularly gathers thousands of scientists and professionals in the visual effects industry, and its technical program is the most prestigious and selective in the field. On the left, he opens the fast forward, a 30 second presentation for each of the accepted papers.

Computers & Graphics: Orthogonal Slicing for Additive Manufacturing


© Kristian Hildebrand

Most additive manufacturing technologies work by layering, i.e. slicing the shape and then generating each slice independently. This introduces an anisotropy into the process, often as different accuracies in the tangential and normal directions, but also in terms of other parameters such as build speed or tensile strength and strain. We model this as an anisotropic cubic element. Our approach then finds a compromise between modeling each part of the shape individually in the best possible direction and using one direction for the whole shape part. In particular, we compute an orthogonal basis and consider only the three basis vectors as slice normals (i.e. fabrication directions). Then we optimize a decomposition of the shape along this basis so that each part can be consistently sliced along one of the basis vectors.

In simulation, we show that this approach is superior to slicing the whole shape in one direction, only. It also has clear benefits if the shape is larger than the build volume of the available equipment.