Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-04-07
2001-08-07
Vo, Cliff N. (Department: 2772)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C345S440000, C345S182000
Reexamination Certificate
active
06271861
ABSTRACT:
The present invention relates generally to methods and systems for shading computer generated images and more particularly to methods and apparatus for shading objects displayed on a raster output device.
BACKGROUND OF THE INVENTION
In many computer systems, it is common to represent and convey information to a user through digital images. These images may take a variety of forms such as alphanumeric characters, graphics and other pictorial representations. The digital images may be conveyed to a user on a raster or continuous tone display device, such as a video monitor, printer and the like. Typically, the digital images are stored in digital form, manipulated and then displayed.
Digital images are generally stored as a geometric description of a scene. The description can be manipulated by the user, then converted to digital raster image data for display. How a two or three dimensional object appears when it is displayed to a user depends on numerous factors including the types of light sources illuminating the object; the object's properties including color, texture and reflectance; and the object's position and orientation with respect to the light sources, the viewer and other surfaces which may reflect light on the object.
It is often desirable to present objects for display in color. In conventional display systems, color may be applied to a region by defining a single color for the entire region (a “flat” coloring), or to add realism, a plurality of colors may be employed. A transition between colors across the surface of an object is referred to as a color gradient. In. order to display a realistic image, a smooth transition between colors across painted areas is required.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a method for defining a smooth shading across an object for display on a raster output device and includes converting the object to a mesh, rendering the mesh, displaying the object having a shading defined by the mesh and editing the mesh until a desired result is achieved in the displayed object.
Aspects of the invention include numerous features. The step of converting the object into a mesh may include determining a boundary for the object enclosed by a boundary box having four corners, determining four points on a boundary of the object that are closest to the four corners of the boundary box, determining four edges on the boundary of the box that connect the four corners, constructing a mesh from the four edges and four corners on the boundary of the object resulting in a single patch mesh including four mesh points corresponding to the four corner point on the boundary, selecting a shading procedure and determining colors to the four mesh points.
The step of determining colors may include receiving a user selection for the colors. The method may further include receiving a user selection to define the number and arrangement of patches in the mesh where the mesh is of to be of form the form of an N×M matrix of patches, subdividing the mesh at N−1 regular intervals in a u direction of the mesh and subdividing the mesh at M−1 regular intervals in a v direction of the mesh.
The shading procedure may determine the colors by receiving a color selection for each corner from a palette of available colors where the selection is performed by the user. The shading procedure may determine the colors by sampling the object at locations corresponding to the mesh points.
One or mor edges of the boundary for the object may include multisegment cubic Bezier curves and the step of constructing a mesh may include constructing boundary edges for the mesh where the boundary edges are multisegment cubic Bezier curves having an identical number of segments as their corresponding edge in the boundary.
The step of editing the mesh may include adding mesh points and defining colors for mesh points resulting in the uniform subdivision of the mesh at the new mesh point. The step of editing the mesh includes one of adding a mesh point, deleting a mesh point, adjusting a mesh point tangent, moving a mesh point, and changing the color of a mesh point.
In another aspect, the invention provides a computer program, tangibly stored on a computer-readable medium, for rendering a two dimensional (2D) patch associated with an object to achieve a smooth shading across the object where the 2D patch defines a complex gradient including at least one foldover edge. The computer program includes instructions for causing a computer to convert the object to a mesh, render the mesh, display the object having a shading defined by the mesh and edit the mesh until a desired result is achieved in the displayed object.
In another aspect, the invention provides a method for defining a smooth shading across an object for display on a raster output device where the object includes a boundary comprising edges at least one of which is a multisegment curve. The method includes converting the object to a mesh including creating a mesh boundary that includes edges that include a same number of segments as a corresponding edge in the boundary of the object, rendering the mesh, displaying the object having a shading defined by the mesh and editing the mesh until a desired result is achieved in the displayed object.
In another aspect, the invention provides a method for defining a gradient across an object for display on a raster output device where the object includes a boundary comprising multisegment edges. The method includes converting the object to a mesh including creating a mesh boundary that follows a geometry of the boundary of the object and creating a series of patches defining the gradient where patch boundaries correspond to segment vertices in the multisegment edges of the boundary for the object.
In another aspect, the invention provides a method for defining a gradient across an object for display on a raster output device where the object includes a boundary comprising multisegment edges. The method includes selecting the object, finding the boundary for the object, creating a bounding box including four corners that encloses the object boundary, identify four points on the boundary of the object that are closest to the four corners of the boundary box, constructing a single patch mesh from the four points and segments connecting pairs of the four points and dividing the single patch mesh to create a series of patches defining the gradient where patch boundaries correspond to segment vertices in the multisegment edges of the boundary of the object.
The invention includes numerous advantages. The present invention provides a mechanism to easily construct complex gradients for use in the display of two dimensional images. These and other advantages may be readily apparent from the detailed description and claims provided below.
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George Paul A.
Sargent Robert S.
Adobe Systems Incorporated
Fish & Richardson P.C.
Vo Cliff N.
LandOfFree
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