Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1997-09-22
2001-01-30
Powell, Mark R. (Department: 2779)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C345S423000, C345S424000, C345S426000
Reexamination Certificate
active
06181348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to volume rendering. More particularly, it relates to a method for rendering volume data as texture maps on top of polyhedral surfaces.
2. Prior Art
Visualization of large volumetric datasets frequently requires the selection of subsets in order to discard unnecessary or obstructing information. Volume rendering offers two ways of selecting: one is to choose the opacity mapping functions appropriately, and the other is to use clipping planes. These two methods, however, are not always sufficient. For example, if the region of interest (ROI) to be rendered is embedded inside data of similar features, and its shape is not convex, it cannot easily be isolated by using clipping planes.
Surface shaded display (SSD) or surface shaded volume rendering are other methods that are used for volume rendering. SSD generally requires 3D texture acceleration hardware that is only available on very expensive machines.
Another alternative for image evaluation is segmentation. Segmentation is a division of the complex picture into parts corresponding to regions or object. For data sets that have a low signal to noise ratio, or for embedded ROIs, segmentation is not always an applicable alternative. Binary segmented surfaces also lack information that is available in the volume dataset.
SUMMARY OF THE INVENTION
A method for rendering volume data as texture maps on top of polyhedral surfaces is provided. Initially, a region of interest (roi) to be rendered must be selected. The selection of a region of interest is done using simple segmentation. The polyhedral surface of this segmentation is used to sample the volume data at a specified depth. The result of the sampling is converted into texture maps that are rendered on the segmented surface.
The present method only uses data close to the surface of the object being rendered, and therefore eliminates concern about distortion generated from resampling. It also enables the selection of various mapping procedures (e.g., maximum intensity projection, minimum intensity projection, etc.) to increase rendering details and show different features depending on the particular application.
In an illustrative embodiment, the method can be used to show structures that are close to a selected surface, enhance a segmented surface, or evaluate the wall thickness of organs (e.g., colon, trachea). It provides more control over the volume to be visualized, and enables the mapping of the volume inside, as well as outside onto the surface. The rendering of an organ wall of an organ which has air inside can also be performed by this method. To do this, the outside of the organ wall/air surface is sampled and then mapped onto the polyhedral surface representation of the same.
Since the texture calculation can be done in a preprocessing step, the rendering is interactive on a graphic platform with 2D texture hardware support. For example, the display, rotation, and translation can be performed in real time when 2D texture acceleration hardware is available.
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Good-Johnson Motilewa
Paschburg Donald B.
Powell Mark R.
Siemens Corporate Research Inc.
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