I graduated on May of 2007 and am currently working in a
startup company in Boston area. My earlier research (during doctoral days)
focused on improving outdoor vision in bad weather such as rain and snow. Rain
and snow create sharp intensity fluctuations in images and videos, which degrade
the performance of many outdoor vision algorithms such as feature tracking,
segmentation, object recognition and tracking. My thesis work focused on handing
rain. The main goal was to understand the visual effects produced by rain and
develop models that lead to simple and effective algorithms for handling rain in
images and videos and for its photorealistic rendering in graphics.
Based Splashing of Water Drops,"
Splashing of water drops is one of the visually fascinating phenomena
and capturing their interaction with scene elements is important in
achieving realism. Splashing results from complex interactions between the
drop and the material it impacts, which makes it hard to model
analytically. This work takes an empirical approach. We measure the
splashing behaviors of 22 common real word material and use it to develop
a stochastic model for splash distribution. Our model is built upon
empirical models previously developed in fluid dynamics and meteorology
and only requires few parameters for generating splashes. User can tune
the parameters to create novel splashes or combine different materials to
generate physically plausible splashes for novel materials. The model is
applicable for rendering splashes due to rain as well as water drops
falling from large heights such as windowsills, trees, and rooftops.
Photorealistic rendering of rain streaks with lighting and viewpoint
effects is a challenging problem.
Raindrops undergo rapid shape distortions as they fall, a phenomenon
referred to as oscillations. The
interaction of light with the oscillating raindrops produces complex
brightness patterns within a single motion-blurred rain
streak. In this project, we develop a model for rain streak
captures these complex interactions. Using this model we have
developed a rain streak appearance database that contains thousands of
streaks with different oscillation parameters
and viewing and lighting directions.We
have developed an efficient image-based rendering algorithm
uses our streak database to add rain to a single image or a captured
video with moving objects and sources. Our rendering results show that
the proposed physically-based rain
streak model greatly enhances the visual realism of rendered rain.
Rendering of Rain Streaks,"
[Implemented in Microsoft SDK 10] (search topic rain )
visibility of rain depends on various factors, such as, the
camera parameters, the properties of rain and the brightness of the
analysis shows that the properties of rain – its small drop
high velocity and low density – make its visibility strongly
on camera parameters such as exposure time and depth of field. In this
project, we demonstrate how these parameters can be selected so as to
reduce or even remove the effects of rain without altering the
appearance of the scene. The proposed method serves to make vision
algorithms more robust to rain without any need for
|"When Does a Camera See Rain?,"
project we conduct a comprehensive analysis of the
visual effects of rain on an imaging system. This analysis includes a
correlation model that captures the dynamics of rain and a
physics-based motion blur model that captures the photometry of rain.
Based on these models, we have developed simple and efficient
algorithms for detecting and removing rain from videos. The
effectiveness of our algorithms is demonstrated via experiments on
videos of complex scenes with moving objects and time-varying textures.
The techniques presented here can be used in a wide range of
applications including video surveillance, vision based navigation,
video/movie editing and video indexing/retrieval.
of Rain from Videos,"
reflects both scene radiance and environmental illumination towards an
We have developed geometric and photometric models for refraction
specular and internal) from, a rain drop. Our geometric and photometric
show that each rain drop behaves like a wide-angle lens that redirects
light from a large field of view of
towards the observer. Hence, each raindrop produces a wide
angle view of the environment thus acting as a natural omni-directional
imaging system. Our models provide important optical properties of
raindrop which are useful for analyzing the appearance of rain.
"Appearance of a Raindrop,"