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# Polygonal Data Comparative Method

IP.com Disclosure Number: IPCOM000014256D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 4 page(s) / 82K

IBM

## Abstract

Disclosed is a system for comparing three-dimensional surface model data by polygonal representation, from the viewpoint of their similarity. The system allows rapid comparison with little calculation when the comparison targets are surface models of thin, plate-shaped objects such as slabs or molded parts of a machine. It also allows the detection of regions in which each of the compared surface models has a different shape. The system consists of three main procedures: 1. Calculate a parameter based on the distance between a reference plane and a sampling point on the surface of the model. 2. Calculate the parameter for each sampling point on each model iteratively, and calculate the sum of the differences between the parameters' values at each pair of sampling point. This summation shows the indifference shape between the compared surface models.

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Polygonal Data Comparative Method

Disclosed is a system for comparing three-dimensional surface model data by polygonal
representation, from the viewpoint of
their similarity. The system allows rapid comparison with little calculation when the
comparison targets are surface models
of thin, plate-shaped objects such as slabs or molded parts of a machine. It also allows
the detection of regions in which
each of the compared surface models has a different shape.

The system consists of three main procedures:

1. Calculate a parameter based on the distance between a reference plane and a sampling point on
the surface of the model.

2. Calculate the parameter for each sampling point on each model iteratively, and calculate the
sum of the differences between the parameters' values at each pair of sampling point. This
summation shows the indifference shape between the compared surface models.

3. Subtract the value of the parameter on one surface from that on the other surface for each
sampling point, and then map the result to a point on a difference map. This map shows the
regions in which the surface models have different shapes.

Procedure: 1. Parameter calculation at each sampling point

a) Set a reference plane for the target surface models. The same reference plane is applied to
both of the compared
surface models, A and B. Arrange a sufficient number of sampling points Pj (j = 0, 1, 2, 3
...) on the reference plane,
according to a certain rule.

b) For the surface model A, calculate...