Name      : Prof. Dr. Rahmita Wirza O.K. Rahmat
Address   : Department of Multimedia
                  Fakulti Sains Komputer dan Teknologi Maklumat
                  Universiti Putra Malaysia, UPM,
                  43400, Serdang, Selangor Darul Ehsan, Malaysia
Tel : 03-8947-1704
Fax : 03-8946-6576

I received my B.Sc. and M.Sc. degrees in Science Mathematics from University Science Malaysia, in 1989 and 1994, respectively. During 1989 to 1990, I am working as research assistance in Department of Physics in University Science Malaysia experimenting on Ozone layer measurement at the Equatorial region, before working as tutor in Universiti Putra Malaysa. I received my PhD in Computer Assisted Engineering from University of Leeds, U.K. At this moment I am working in Faculty of Computer Science and Information Technology as lecturer (Associate Prof in Computer Graphics). Among my focus research area are Computer Graphics, Computer Assisted Surgery and Computational Geometry.

o    Computer Integrated System in Health
o    Geometric Modeling and Augmented Reality
o    Geometrical Reverse Engineering


The accurate measurement of complex surfaces is difficult. Accuracy demands precision in measuring technology, i.e., the measuring machine and also precise mathematical representation of complex geometries.
This thesis introduces a method of measuring a complex surface by using a Coordinate Measuring Machine and in this case representing the measured surfaces mathematically. This enables comparison with other surfaces, e.g. the as-designed surface or the original unworn surface. The measurement of the knee prosthesis was taken as a case study.
To measure accurately the complex surface, this thesis proposes a method based on  a surface fitting technique. There are several techniques available, such as Bézier, B-Spline and NURBS, and in this case, the author has decided to choose the Bézier technique. In order to represent the complex surface with minimum measuring points, the author has chosen the technique of surface interpolation of scattered data and due to the complexity of the shape it is better to use triangular patches than rectangular patches. The work is an extension and combination of techniques suggested by Goodman and Said.
The need to measure accurately the amount of wear particles released from the knee joint implanted during operation within the human body is becoming important. This amount of wear is critical to the life expectancy of the joint.  By accurately measuring the knee joint surface and subsequently determining the small difference between the measurements before and after wear testing, the volume of material can be calculated.
The main objective of this research is accurately to measure and represent a complex surface, e.g. the surface of the knee joint prosthesis, so that minimal changes of the surface can be detected. The author has produced a planning strategy for the measurement. This proposed plan involves taking several points on the knee, using the fitting technique to produce a set of points and producing a CMM program which can measure one whole knee for each different design. This proposed measurement plan also involves approximating the original surface of the ex-plant, because in most cases, the surgeon does not have a blue-print or original design for the knee joint.