Apparatus and method for relating a point of selection to an object in a graphics display system
First Claim
1. In a system for rendering images composed of three dimensional objects on a video display, apparatus for picking a visible object, comprising:
- a Z buffer for storing displayed image depth data;
means for defining a pick window with a pick window boundary;
means for selectively rerendering each previously displayed object, including calculating object depth data, when a region encompassing and larger than said object intersects the pick window boundary; and
means for detecting each visible object in the pick window by comparing the displayed image depth data in the Z buffer to the object depth data for each selectively rerendered object to determine whether the displayed image depth data matches the object depth data.
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Abstract
Apparatus and methods for picking three dimensional objects from images depicted on a video display. The displayed objects are selectively rerendered. During such rerendering the object pixels are compared in depth to the data in a Z buffer for determining visibility. The number and size of the objects subject to rerendering by the rasterization processor is constrained by using the front end graphics processor to define object extents and by rerendering only extents which have been clipped to the boundaries of the pick window. The rerendering operation does not alter the three dimensional graphics image stored in and repetitively scanned from the frame buffer. Selection between multiple objects within the pick window can include a weighted comparison using a pick plane memory to store visibility data by object.
58 Citations
12 Claims
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1. In a system for rendering images composed of three dimensional objects on a video display, apparatus for picking a visible object, comprising:
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a Z buffer for storing displayed image depth data; means for defining a pick window with a pick window boundary; means for selectively rerendering each previously displayed object, including calculating object depth data, when a region encompassing and larger than said object intersects the pick window boundary; and means for detecting each visible object in the pick window by comparing the displayed image depth data in the Z buffer to the object depth data for each selectively rerendered object to determine whether the displayed image depth data matches the object depth data. - View Dependent Claims (2, 3, 4)
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5. A video display system for picking visible objects from rendered three dimensional objects, comprising:
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a frame buffer for storing displayed image data of rendered three dimensional objects; a Z buffer memory for storing displayed image depth data of rendered three dimensional objects; a plane memory for storing data representing windows used in rendering the displayed image data stored in the frame buffer; means for storing object boundary data corresponding to each object which encompasses and is larger than each corresponding object; means for defining a pick window with a pick window boundary; a front end processor means for identifying each object which has object boundary data that intersects the pick window; and a rasterization processor means for rerendering each identified object to identify which rerendered objects have object depth data that matches the displayed image depth data. - View Dependent Claims (6, 7, 8, 9)
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10. A process for picking a visible object from multiple three dimensional objects rendered on a graphics video display, comprising the steps of:
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defining a pick window boundary; identifying objects within the pick window by comparing object boundaries to pick window boundaries, each object boundary corresponding to an object wherein each object boundary encompasses and is larger than each corresponding object; selectively rerendering said identified objects; and detecting visible objects by matching the depth of the rerendered objects with the depth data for corresponding pixel positions within the pick window boundary. - View Dependent Claims (11, 12)
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Specification