Finally, we want to point out another consider-
ation related to the mobile GPU architectures used
in our experiments. PowerVR graphics processors
heavily rely on a method called Tile Based Deferred
Rendering (TBDR) (Power VR, 2011) to achieve
good rendering performance while keeping low en-
ergy consumption. TBDR allows to perform hidden
surface removal before fragments are processed thus
avoiding unnecessarily computations. Unfortunately,
this hardware optimization is not well suited for vol-
ume rendering. The texture slicing technique requires
blending, which forces to process all fragments. In
our experiments, turning off blending boosted the per-
formance to 60 fps regardless of the number of slices
rendered. The raycasting technique does not bene-
fit from this technique because there is no fragments
overlap so no computation can be avoided.
6 CONCLUSIONS
We have developed a novel volume rendering algo-
rithm perfectly suited to modern GPU-enabled mobile
devices. This proposal has addressed the limitations
of these devices, mainly the lack of 3D texture sup-
port and the limited complexity that can be imbued to
shaders. Our method has been tested under different
devices and scenarios. We have also compared our
results with the volume ray casting method. In gen-
eral, our experiments show that the ray-based method
provides a slightly higher quality image, whereas our
texture slicing method doubles the frame rate.
Our work has shown that mobile devices consti-
tutes a valid platform to achieve interactive volume
visualization, despite the fact that the rendering ca-
pabilities are reduced in comparison to desktop solu-
tions, due to their inherent autonomy limitations.
As future work, our current research is focused on
the improvement of the rendering performance and
quality based on a continuous search of new tech-
niques well suited to this kind of devices. We also
plan to improve the visual appearance by including
complex illumination in our models.
In addition, we plan to use our experience and this
technology in university teaching, for instance in sub-
jects like human anatomy, diagnosis, etc. We believe
that interactive visualization of medical data in hand-
held devices can be a worthy pedagogic instrument.
ACKNOWLEDGEMENTS
This work has been partially supported by the
Ministerio de Ciencia e Innovaci
´
on and the Euro-
pean Union (via ERDF funds) through the research
project TIN2011-25259 and by the University of Ja
´
en
through the projects PID441012 and UJA2010/13/08
sponsored by Caja Rural de Ja
´
en.
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