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Rendering Algorithm for Visualizing Voxel And Surface Data

IP.com Disclosure Number: IPCOM000100338D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 4 page(s) / 142K

Publishing Venue

IBM

Related People

Miyazawa, T: AUTHOR [+2]

Abstract

Disclosed is a new rendering algorithm for visualizing volumes consisting of voxel and surface data by processing both types of data in a unified way. The algorithm is very versatile and effective in interpreting three-dimensional volumetric data that include three-dimensional geometric objects, and continuously covers the gap between surface and volume rendering techniques.

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Rendering Algorithm for Visualizing Voxel And Surface Data

       Disclosed is a new rendering algorithm for visualizing
volumes consisting of voxel and surface data by processing both types
of data in a unified way. The algorithm is very versatile and
effective in interpreting three-dimensional volumetric data that
include three-dimensional geometric objects, and continuously covers
the gap between surface and volume rendering techniques.

      A very effective approach to volume visualization is volume
rendering, in which voxels in the volume are directly displayed,
without any intermediate conversion of voxel data to polygonal
surfaces before being rendered on the screen. Visualization by volume
rendering can easily produce various images by controlling the
relative amounts of color and opacity corresponding to voxel data.
Therefore, volume rendering is very appropriate for exploratory work,
and especially for use by scientists. However, it is not suitable for
displaying three-dimensional geometric models that define the shapes
of objects, because of the low resolution of the rendered models and
the computational cost in rendering.

      Most three-dimensional volumetric data generated in
applications, such as computer simulations, scientific experiments,
and sophisticated observations, include three-dimensional objects.
Therefore, it is indispensable to visualize three-dimensional
volumetric data composed of voxels, and three-dimensional objects
composed of geometric primitives.

      We chose the ray casting method as a global illumination model
for the algorithm so that voxel and surface data can be processed in
a unified way. In the algorithm, voxel data defined in a
three-dimensional orthogonal regular or irregular grid and surface
data composed of polygons are processed.

      Fig. 1 shows an example of the data structure used in the
algorithm. Fig. 2 shows a flow chart of the algorithm. After
preprocessing, the process continues until either the voxel is
exhausted, the accumulated opacity reaches unity, or the ray
intersects with an opaque polygon. The main steps of the algorithm
are as follows:
      1. Voxel-polygon list
     As a pre-process, the voxel-polygon lists are composed. Each
polygon is inserted into voxels with simple minimum/maximum
operations between the bounding box of the polygon and the
three-dimensional grid in which the voxel data are defined.  The
voxel-polygon lists allow efficient calculation of ray-polygon
intersections.
      2. Identification of the first voxel intersected by the ray
After the pre-process, a ray parameterized by O+Dt is cast into the
volu...