International Business Machines Corporation

Ryutarou Ohbuchi

Masaki Aono

Hiroshi Masuda

Kazuya Shimizu

Shigeo Murohashi

A data compression method for processing topological structures of various geometric models. A topological transformation is performed for a three-dimensional (3D) geometric model that is to be compressed, and a triangle mesh is generated. A conventional triangle mesh compression method is employed. Associated data required for the performance of a reverse operation for the topological transformation are prepared. As a result, topological data for the 3D geometric model is compressed. As needed, the data for the compressed triangle mesh and associated operation data are output. Furthermore, a necessary process (e.g., a compression process) is also performed for geometric data for the 3D geometric model, and the resultant data are either stored or output. For the decompression of compressed data, the compressed triangle mesh is decompressed using the method employed for compression, and a triangle mesh is generated. The associated data are then employed to perform the reverse operation for the topological transformation of the triangle mesh, and the topological data for the original 3D geometric model are recovered. If the geometric data are also compressed, they are decompressed and are employed with the topological data to recover the 3D geometric model.

Method and apparatus for compressing and transmitting a three-dimensional geometric model

Information is embedded in a three-dimensional geometric model in a visible or invisible state by changing geometric parameters of a three-dimensional geometric model. The three-dimensional geometric model comprises polyhedrons, lines, a set of points, or curved surfaces which are primitives (components) of the model. Each primitive is defined by a geometric parameter. The geometric shape of a three-dimensional geometric model is defined by a set of many geometric parameters. The information is embedded by changing the geometric parameters of a plurality of primitives constituting a three-dimensional geometric model.

Embedding information in three-dimensional geometric model

The present invention is directed to a real-time controllable reflection mapping function which covers all stereoscopic directions of space. More specifically, the surface of a mirrored object is segmented into a plurality of polygonal elements (for example, triangles). Then, a polyhedron, which includes a predetermined point (for example, the center of the mirrored object) in a three-dimensional space (for example, a cube) in the interior thereof, is generated and a rendering process is performed for each surface of the polyhedron with the predetermined point as a view point. The rendered image is stored. Thereafter, a reflection vector is calculated between each vertex of the polygonal elements and a view point used when the entire three-dimensional space is rendered. Next, the surface of the polyhedron, in which an intersecting point between the reflection vector with the predetermined point as a start point and the polyhedron exists, is obtained. The coordinate in the image, which corresponds to each vertex of the polygonal elements, is calculated by using the surface where the intersecting point exists and the reflection vector. The image is texture-mapped onto the surface of the object by using the coordinate in the image which corresponds to each vertex of the polygonal elements. Finally, the result of the texture mapping is displayed.

Rendering method and apparatus

In order to render a three-dimensional space which has a spotlight source with a cone angle .theta. at high speed and with better quality, an object's surface in the three-dimensional space is first meshed into a plurality of elements. Then, a radiosity from the spotlight source is calculated for each element which is included inside of the cone angle .theta. when viewed from the spotlight source. Thereafter, an intensity-value at each vertex of each element is calculated from the radiosity calculated for each element. Next, Gouraud shading is performed by using the intensity-value at each vertex of each element, and the result is displayed on a display.

Growing community of inventors

Yokohama, Japan

Ryutarou Ohbuchi