Image display method and apparatus

Claim 2

Image display apparatus comprising: first buffers for storing first depth values for pixel positions on the front boundary surface of a clipping region, each said pixel position having a corresponding first buffer for storing said first depth value, which may differ from the first depth values stored in the other first buffers; second buffers for storing second depth values for said pixel positions on the back boundary surface of said clipping region, each said pixel position having a corresponding second buffer for storing said second depth value, which may differ from the second depth values stored in the other second buffers; means for generating a depth value for a pixel position on an object to be displayed; means for comparing said generated depth value with the first and second depth values stored in the first and second buffers corresponding to said pixel position; and means for determining whether said pixel position on said object to be displayed is within said clipping region in accordance with the results of said comparison by said comparing means.

Claim 3

Image display apparatus comprising: pixel data buffers for storing previously generated pixel data for each pixel position on a screen, each said pixel position having a corresponding pixel data buffer; first buffers for storing first depth values for said pixel positions on the front boundary surface of a clipping region, each said pixel position having a corresponding first buffer for storing said first depth value, which may differ from the first depth values stored in the other first buffers; second buffers for storing second depth values for said pixel positions on the back boundary surface of said clipping region, each said pixel position having a corresponding second buffer for storing said second depth value, which may differ from the second depth values stored in the other second buffers; means for generating new pixel data and a depth value for a pixel position on an object to be displayed; means for replacing the second depth value stored in the corresponding second buffer with said generated depth value and replacing the previously generated pixel data stored in the corresponding pixel data buffer with said new pixel data when said generated depth value represents a distance from the viewpoint that is larger than that represented by the first depth value stored in the corresponding first buffer and smaller than that represented by the second depth value stored in the corresponding second buffer.

Claim 4

Image display apparatus comprising: pixel data buffers for storing previously generated pixel data for each pixel position on a screen, each said pixel position having a corresponding pixel data buffer; first buffers for storing first depth values for said pixel positions on the front boundary surface of a clipping region, each said pixel position having a corresponding first buffer for storing said first depth value, which may differ from the first depth values stored in the other first buffers; second buffers for storing second depth values for said pixel positions on the back boundary surface of said clipping region, each said pixel position having a corresponding second buffer for storing said second depth value, which may differ from the second depth values stored in the other second buffers; means for generating new pixel data and a depth value for a pixel position on an object to be displayed; means for replacing the second depth value stored in the corresponding second buffer with said generated depth value and replacing the previously generated pixel data stored in the corresponding pixel data buffer with said new pixel data when said generated depth value represents a distance from the viewpoint that is larger than that represented by the first depth value stored in the corresponding first buffer and smaller than that represented by the second depth value stored in the corresponding second buffer.

Claim 5

Apparatus as in claim 2, further comprising a flag buffer for indicating for each pixel position whether a first or second depth value on a boundary surface of the clipping region has been stored in the corresponding first or second buffer, said second depth value and previously generated pixel data being replaced only if said flag indicates that a first or second depth value on a boundary surface of the clipping region has been stored in the corresponding first or second buffer.

Claim 6

An image display method including the steps of: storing first depth values for pixel positions on the front boundary surface of a clipping region in first buffers corresponding to said pixel positions, each said pixel position having a corresponding first buffer for storing said first depth value, which may differ from the first depth values stored in the other first buffers; storing second depth values for said pixel positions on the back boundary surface of said clipping region in second buffers corresponding to said pixel positions, each said pixel position having a corresponding second buffer for storing said second depth value, which may differ from the second depth values stored in the other second buffers; generating a depth value for a pixel position on an object to be displayed; comparing said generated depth value with the first and second depth values stored in the first and second buffers corresponding to said pixel position; and determining whether said pixel position on said object to be displayed is within said clipping region in accordance with the results of said comparison.

Claim 7

An image display method including the steps of: storing first depth values for pixel positions on the front boundary surface of a clipping region in first buffers corresponding to said pixel positions, each said pixel position having a corresponding first buffer for storing said first depth value, which may differ from the first depth values stored in the other first buffers; storing second depth values for said pixel positions on the back boundary surface of said clipping region in second buffers corresponding to said pixel positions, each said pixel position having a corresponding second buffer for storing said second depth value, which may differ from the second depth values stored in the other second buffers; generating a depth value for a pixel position on an object to be displayed; comparing said generated depth value with the first and second depth values stored in the first and second buffers corresponding to said pixel position; and determining whether said pixel position on said object to be displayed is within said clipping region in accordance with the results of said comparison.

Claim 8

A method as in claim 4 in which said steps are performed for each of a plurality of pixel positions on a screen.

Claim 9

A method as in claim 4 in which said clipping region is a polyhedron, said front boundary surface comprising at least one front-facing boundary polygon facing the viewpoint, said back boundary surface comprising at least one back-facing boundary surface facing away from the viewpoint.

Claim 10

A method as in claim 6 including the step of projecting a view port onto the planes containing said boundary polygons to form extended boundary polygons.

Claim 11

A method as in claim 4 including the steps of: storing previously generated pixel data for said pixel position in a pixel data buffer; generating new pixel data for said pixel position on said object to be displayed; replacing the second depth value stored in the corresponding second buffer with said generated depth value and replacing the previously generated pixel data stored in said pixel data buffer with said new pixel data when said generated depth value represents a distance from the viewpoint that is larger than that represented by the first depth value stored in said first buffer and smaller than that represented by the second depth value stored in said second buffer.