The present invention is a computer system and method for determining the
closest point on a shape (2 dimensional or 3 dimensional surface) to any
general query point. The system has one or more central processing units
(CPUs), one or more memories, and one or more geometric model portions
stored in one or more of the memories. The geometric model portions have a
plurality of line segments (polygons), each of the line segments
(polygons) being between a first and a second endpoint (having a polygon
boundary). The line segments and end points (polygons and polygon
boundaries) are connected to form a shape (in 3 dimensions, a surface)
with one or more parameters. Parameters can include geometric position,
time, temperature, pressure, flow, color, texture, or any other
descriptive value. A multiresolution process that creates one or more
models of the shape (surface). The models having a hierarchy of
resolutions. Each model has one or more model line segments (model
polygons) that approximate one or more of the line segments (polygons).
Each model line segment (model polygons) is associated with an error. A
distance process, for every model line segment (polygon), determines a
distance between a closest point on one or more of the model line segments
and a query point. The distance represents one or a combination of two or
more of the parameters. The process further determines a confidence level
in terms of an upper bound and a lower bound of an envelope enclosing the
segment (polygon). The closest point is within the envelope--the upper
bound representing an upper limit of the parameter in the envelope
determined by an upper error of the respective model containing the model
line segment and the lower bound representing a lower limit of the
parameter in the envelope determined by a lower error of the respective
model. A priority process orders the model line segments (polygons)
according to their respective lower bounds and if a maximum error for
every one of the model line segments is less than a threshold. The
priority process also selects the smallest distance as the minimum
distance between the query point and the shape.