Research Scholar

ViGIL -- Vision, Imaging and Graphics Laboratory
Department of Computer Science and Engineering
Indian Institute of Technology, Bombay

Phone : +91-2576-4709 (CSE Dept, ViGIL)
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Hi, I am a fourth year postgraduate student, doing my PhD in Department of Computer Science and Engineering at Indian Institute of Technology, Bombay under the supervision of Prof. Sharat Chandran

I welcomed the world with tears on September 10th. I was born and brought up in Bombay, India. I did my junior schooling from PGG English High School. I then went on to complete my diploma in computer technology from Swami Vivekanand Polytechnic and my bachelor's degree in Information Technology from V.D.Patil Institute. I have been lucky enough to top Mumbai University for three consecutive years during my degree program. I was also honoured thrice with the prestigiuos JRD Tata and Ratan Tata Scholarships and a Best Student of the Institute Award-2004 for my accomplishments.

I now proudly stand in Indian Institute of Technology, Bombay as an honoured Infosys Fellow and a research scholar in the field of computer graphics. Pictures and cartoons have always been fascinating to me and may be the primary reason for me being here. Initially liked watching them, then drawing them, and now creating them on computer. Here is a brief bio-data about myself.


Ongoing Research

Point based modeling is a new upcoming technology, where a virtual 3D model is constructed as a set of points acquired from 3D laser scans of real objects, as shown.

Figure::Left: Point models acquired using 3D laser scanners. Right: Point-based representation of a bunny shown at extreme right (Image courtesy The Digital Michelangelo Project)

These models may be scans of cultural heritage structures (for example old temples, caves as shown in figure below) and we may wish to view them in a virtual museum under various lighting conditions. This research will help preserve these models and also helps in adding certain aesthetic value.

Figure: Grottoes, such as the ones from China and India form a treasure for mankind. If data from the ceiling and the statues are available as point samples, can we capture the inter reflections?

Given such models and some light sources around them, we wish to calculate on each of the points of the model, the effect of light directly from the source and indirectly reflected from other points in the model (phenomenon called global illumination as shown below).

Figure: Point models rendered with global illumination effects. Pair-wise visibility information is essential in such cases. Note that the room as well as the models in it are input as point models.

The light transfers between points happen only if the points are visible to each other. Thus, the topic of visibility between points is essential for calculating the effects of global illumination on three-dimensional scanned point models. This problem has been addressed in my paper on Visibility Map for Global Illumination in Point Clouds which was accepted at ACM SIGGRAPH GRAPHITE 2007, the 5th Annual International Conference on Computer Graphics and Interactive Techniques in Australasia and Southeast Asia . The following images are some of the sample results for the same.

Figure: Figure on left shows a point model of an empty Cornell room. Note the default colors of the walls. We now introduce a pink Stanford bunny in the next image. Notice the eye (w.r.t. which visibility is being computed) is on the red wall (on the left), marked with a cyan colored dot. The violet (purple) color indicates those portions of the room that are visible to this eye. Notice the``shadow'' of the bunny on the green wall and on the floor. The same idea is repeated with the eye placed at different locations for the Buddha in the Cornell room

Figure: Figure on the left shows a point model of a different (empty) Cornell room. Note the default colors of the walls. We repeat similar tests with point models of the Indian god Ganesha (second figure), the Indian goddess Satyavati (third figure) and a blue Bunny (extreme right) placed in a Cornell room.

Also,the type of light reflection depends on whether the reflecting object has diffuse or specular reflection property. We have designed a global illumination solution using Fast Multipole Method (FMM) which handles diffuse inter reflections in a scene comprising of 3D scanned point models, and we are now working on specular inter-reflections in a similar scene.

Sample figure: Left: Colors transfer (or "bleed") from one surface to another, an effect of diffuse inter-reflection. Also notable is the caustic projected on the red wall as light passes through the glass sphere. Right: Reflections and refractions due to the specular objects are clearly evident

Further, calculating a global illumination solution is by itself an O(N2)problem, where N are the number of points in the input point model. To speed up this process, we are currently also working on implementing the FMM algorithm for diffuse global illumination on Graphics Processing Unit (GPU), which inherently has a parallel structure of 128 processing elements with shared memory. As a first step for the same, we have designed and implemented a Fast, Parallel, GPU-based Construction of Space Filling Curves and Octrees (one-page abstract) which has been accepted at Symposium on Interactive 3D Graphics and Games (I3D 2008)

Finally, we would like to combine all the above modules into a single system capable of producing all global illumination effects on any given point model scene.

Thats all folks !!

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Last update: Mar, 2008
Rhushabh Goradia