US 6,204,857 B1Granted

Method and apparatus for effective level of detail selection

AssigneeReal 3-D

InventorsThomas A. Piazza, Michael Mantor, Ralph Clayton Taylor, Val Gene Cook

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Abstract

Method and apparatus for rendering texture to an object to be displayed on a pixel screen display. This technique makes use of linear interpolation between perspectively correct texture address to calculate rates of change of individual texture addresses components to determine a selection of the correct LOD map to use and intermediate texture addresses for pixels of the object between the perspectively correct addresses. The method first determines perspectively correct texture address values associated with four corners of a predefined span or grid of pixels. Then, a linear interpolation technique is implemented to calculate a rate of change of texture address components in the screen x and y directions for pixels between the perspectively bound span corners. This linear interpolation technique is performed in both screen directions to thereby create a potentially unique level of detail value for each pixel, which is then used as an index to select the correct pre-filtered LOD texture map. When mapping an individually determined LOD value per pixel, the effect of producing undesirable artifacts that may appear if a single LOD for an entire span or polygon is used, is obviated.

Claims14

Dependent claims

A method for mapping texture information from a texture space to a computer generated object represented as one or more pixel coordinates (x,y) in a computer image display screen space, said texture space including a plurality of texture maps, with each map having texture information associated with a predefined level of detail, said texture information to be mapped in the form of texels, with each texel represented by a texture address coordinate (u,v), said method comprising:

defining a grid of a predetermined number of pixels, said grid extending in both horizontal and vertical dimensions;
for each of a group of the pixels,
1) calculating a perspectively correct texture address for the pixel, and
2) determining a rate of change of texture addresses, at the pixel, in both the horizontal and vertical directions;
and
for each of a defined set of pixels,
1) using linear interpolation techniques and using the calculated texture addresses to determine an approximate rate of change of texture addresses, at said each pixel, in both the horizontal and vertical directions,
2) utilizing the determined approximate rate of changes to compute a level of detail index value, and
3) selecting one of the texture maps based on said computed level of detail index value, and utilizing the calculated texture address for the pixel to select one or more texels in the selected texture map for the pixel;
wherein said calculating step includes calculating at least one perspectively corrected texture value for a pixel located on one corner of said grid, and calculating two more perspectively corrected texture addresses (Uq,r, Vq,r) for pixels located outside said grid adjacent remaining corners of said grid.

7 more elements

Dependencies are inferred from the claim text.