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3 Machine Graphics and Vision

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Warping-based interactive visualization on PC

100%

Li X. , Zheng N.

tom Vol. 8, No. 1

63-76

Image--based rendering produces realistic--looking 3D graphics at relatively low cost. In this paper, an original post--warping redering system using more than two sample views to derive a new view is presented. Owing to the warp--based compression and incremental coputation, the computational expense is less or no more than conventional two-image synthesis approaches. The procedure consists of three steps. First, a set of sample images is selectively acquired with conventional geometry rendering or volume rendering or from photographs of the real scene. Next each of the neighboring image pair is compressed by warping transformation based on redundant pixels between them. Finally, the compressed sample images are directly re- projected to produce new images. In order to improve the speed more, an incremental warping flow is developed, which is computationally less expense. With the method described above, animation faster than fifty frames (300x 300) per second is achieved on PC.

Light field rendering of dynamic scene

80%

Li W. , Ke Q. , Huang X. , Zheng N.

tom Vol. 7, No. 3

551-563

Image based rendering has displayed advantage in speed over traditional geometry based rendering algorithms. With the four dimensionl light field descriptions, static scene can be generated with interactive rate on ordinary computer. The limitation of the scheme is that it can only handle static scene and fixed illumination. This paper raises the idea to decompose the light field into sub-light-fields that do not change as scene changes. It expands the advantage of light field rendering to dynamic scenes where the position and orientation of objects, lights and viewpoint can be modified arbitrarily. The sub-light-fields include: ambient light field and spot light field. The latter is actually an eight-diamensional space. Because diffuse reflection is idenpendent on view direction, this paper presents a four-diamensional representation of spot light field. Considering the linearity of diffuse reflection to different spot light, the spot light fields of an object can be represented by the reflection light field to a pure-color light with unit intensity, to decrease storage and preprocessing. Owing to the coherency in thier data structures, data of the corresponding point in the ambient light field, diffuse light field and depth field are combined into a 5-dimensional vector which can be compressed efficiently with vector quantization. The algorithm given in this paper accurately computers typical characteristics of dynamic scene such as changes in surface color and shadow.

Image coding based on flexible contour model

80%

Zheng N. , Song W. , Li W.

tom Vol. 8, No. 1

83-94

This paper presents a new scheme of model-based image coding method. First a new image model called Flexible Contour Model that can extract features of nonrigid objects in images is proposed, then we deduce the fast algorithms for calculating the parameters of the model and for matching the model to images. Furthermore the combination of the model with multiscale analysis and the triangulation of the model has been studies. As a result, reconstrution of orginal images with high compression rate and unnaticeable distortion was obtained.