Eurographics 2006 Practice Talks

Thursday, August 31st, 14:00-16:10, room 019

14:00 - Fastforward Slides
14:10 - Johannes G\uffffnther. Ray Tracing Animated Scenes using Motion Decomposition.
14:50 - Kaleigh Smith and Grzegorz Krawczyk. Beyond Tone Mapping: Enhanced Depiction of Tone Mapped HDR Images.
15:30 - Akiko Yoshida. Analysis of Reproducing Real-World Appearance on Displays of Varying Dynamic Range.

Abstracts

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Ray Tracing Animated Scenes using Motion Decomposition
Johannes G\uffffnther, Heiko Friedrich, Ingo Wald, Hans-Peter Seidel, Philipp Slusallek
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Though ray tracing has recently become interactive, its high
precomputation time for building spatial indices usually limits its
applications to walkthroughs of static scenes. This is a major
limitation, as most applications demand support for dynamically animated
models. In this talk, I present a new approach to ray trace a special
but important class of dynamic scenes, namely models whose connectivity
does not change over time and for which all possible poses are known in
advance.

We support these kinds of models by introducing two new concepts: motion
decomposition, and fuzzy kd-trees. We analyze the animation and break
the model down into submeshes with similar motion. For each of these
submeshes and for every time step, we calculate a best affine
transformation through a least square approach. Any residual motion is
then captured in a /single/ "fuzzy kd-tree" for the entire animation.

Together, these techniques allow for ray tracing animations /without/
rebuilding the spatial index structures for the submeshes, resulting in
interactive frame rates of 5 to 15 fps even on a single CPU.

------------------------------------------------------------------------------Beyond Tone Mapping: Enhanced Depiction of Tone Mapped
HDR Images
K. Smith, G. Krawczyk, K. Myszkowski, H-P. Seidel
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In this work we take a non-standard approach to the problem of depicting HDR images for LDR display. Instead of developing yet another
algorithm, we provide the means to enhance the depiction of an HDR image produced by an arbitrary tone mapping algorithm, thus
restoring original contrast information. Based on experience and conclusions from previous work we identify Global Contrast Change and
Detail Visibility Change as the two major tone mapping distortions, and we create objective perceptual metrics to measure these
contrast distortions between an HDR image and its LDR depiction. Driven by these metrics, we present techniques for creating enhanced
images that restore the original HDR contrast information with colour contrast achieved by chroma scaling. The increased colour
contrast augments detail visibility, and countershading encourages the prominence of foreground objects, thus reclaiming the loss in
perceived global contrast.

------------------------------------------------------------------------------Analysis of Reproducing Real-World Appearance on
Displays of Varying Dynamic Range
Akiko Yoshida, Rafal Mantiuk, Karol Myszkowski, Hans-Peter Seidel
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We conduct a series of experiments to investigate the desired
properties of a tone mapping operator (TMO) and to design such an
operator based on subjective data. We propose a novel approach to
the tone mapping problem, in which the tone mapping parameters are
determined based on the data from subjective experiments, rather
than an image processing algorithm or a visual model. To collect
this data, a series of experiments are conducted in which the
subjects adjust three generic TMO parameters: brightness, contrast
and color saturation. In two experiments, the subjects are to find
a) the most preferred image without a reference image (preference
task) and b) the closest image to the real-world scene which the
subjects are confronted with (fidelity task). We analyze subjects'
choice of parameters to provide more intuitive control over the
parameters of a tone mapping operator. Unlike most of the researched
TMOs that focus on rendering for standard low dynamic range
monitors, we consider a broad range of potential displays, each
offering different dynamic range and brightness. We simulate
capabilities of such displays on a high dynamic range (HDR) display.
This allows us to address the question of
how tone mapping needs to be adjusted to accommodate displays with
drastically different dynamic ranges.