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Essa, Irfan

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Exemplar Based Non-parametric BRDFs

2002 , Haro, Antonio , Essa, Irfan

Realistic rendering of computer modeled three dimensional surfaces typically involves building a parameterized model of the bidirectional reflectance distribution function (BRDF) of the desired surface material. We present a technique to render these surfaces with proper illumination and material properties using only a photograph of a sphere of the desired material under desired lighting conditions. Capitalizing on the fact that the geometry of the material in the photograph is known, we sample pixels of the sphere's reflectance to create photo-realistic renderings of computer models with the same material properties. The reflectance is sampled using texture synthesis techniques that compensate for the fact that very little of the BRDF observed in the photograph is known. The technique uses the limited observations of the function to create a plausible realistic rendering of the surface that can be composited onto a background plate easily.

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Head Tracking using a Textured Polygonal Model

1998 , Schodl, Arno , Haro, Antonio , Essa, Irfan

We describe the use of a three-dimensional textured model of the human head under perspective projection to track a person's face. The system is hand-initialized by projecting an image of a face onto the polygonal head model. Tracking is achieved by finding the six translation and rotation parameters to register a rendered image of the textured model with the video image. We find the parameters by mapping the derivative of the error with respect to the parameters to intensity gradients in the image, use a robust estimator to pool the information and do gradient descent.

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Real-time, Photo-realistic, Physically Based Rendering of Fine Sacle Human Skin Structure

2001 , Haro, Antonio , Guenter, Brian K. , Essa, Irfan

Skin is noticeably bumpy in character, which is clearly visible in close-up shots in a film or game. Methods that rely on simple texture-mapping of faces lack such high frequency shape detail, which makes them look non-realistic. More specifically, this detail is usually ignored in real-time applications, or is drawn in manually by an artist. In this paper, we present techniques for capturing and rendering the fine scale structure of human skin. First, we present a method for creating normal maps of skin with a high degree of accuracy from physical data. We also present techniques inspired by texture synthesis to "grow" skin normal maps to cover the face. Finally, we demonstrate how such skin models can be rendered in real-time on consumer-end graphics hardware.

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Detecting and Tracking Eyes by Using their Physiological Properties, Dynamics and Appearance

1999 , Haro, Antonio , Flickner, Myron , Essa, Irfan

Reliable detection and tracking of eyes is an important requirement for attentive user interfaces. In this paper, we present a methodology for detecting eyes robustly in indoor environments in real-time. We exploit the physiological properties and appearance of eyes as well as head/eye motion dynamics. Structured infrared lighting is used to capture the physiological properties of eyes, Kalman trackers are used to model eye/head dynamics, and a probabilistic based appearance model is used to represent eye appearance. By combining three separate modalities, with specific enhancements within each modality, our approach allows eyes to be treated as robust features that can be used for other higher-level processing.

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