10. 3D Coordinate Operations Assoc.Prof.Dr. Ahmet Zafer Şenalp Mechanical Engineering Department Gebze Technical University ME 521 Computer Aided Design

Introduction Most of the problems needs 3D computer graphics for descrition. For this purpose 3D Trasnformations or coordinate operations are used. 3-D Transformations:  Translation  Rotation  Scaling Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations

T x, T y, T z are the components of the translation in x, y, z, in object coordinates Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations

Through point (0, 0, 0) and about x axis, by the angle  counterclockwise when looked from +x: Below figure shows +X and –X rotation directions (+y rotation direction) Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations İnitial state +X rotation -X rotation

Below figure shows +X +Y, and +Z rotation directions. Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations İnitial state +X rotation +Y rotation +Z rotation

Transformation matrices for rotation: Rotation about X axis: Rotation about Y axis: Rotation about Z axis: Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations

Transformation matrix for scaling: In below figure mirror images of two objects are onbtained by scaling. Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations

Inverse transforms are obtained by placing negative values: Inverse of Translation: Inverse of Rotation abou X: Inverse of Rotation about Y: Inverse of Rotation about Z: Inverse transform of T matrix is represented by T -1. Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations

or Concatenation of operations: Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations

Performing the procedure must comply with the order of concatenation operations. Below example shows the difference between rotations about first +X and then +Y and the reverse. Dr. Ahmet Zafer Şenalp ME Mechanical Engineering Department, GTU 10. 3D Coordinate Operations İnitial state +X rotation İnitial state +Y rotation +X rotation