If a transformation of the plane T1 is followed by a second plane transformation T2, then the result itself may be represented by a single transformation T which is the composition of T1 and T2 taken in that order. This is written as T = T1∙T2.
Composite transformation can be achieved by concatenation of transformation matrices to obtain a combined transformation matrix.
A combined matrix −
[T][X] = [X] [T1] [T2] [T3] [T4] …. [Tn]
Where [Ti] is any combination of
The change in the order of transformation would lead to different results, as in general matrix multiplication is not cumulative, that is [A] . [B] ≠ [B] . [A] and the order of multiplication. The basic purpose of composing transformations is to gain efficiency by applying a single composed transformation to a point, rather than applying a series of transformation, one after another.
For example, to rotate an object about an arbitrary point (Xp, Yp), we have to carry out three steps −
- Translate point (Xp, Yp) to the origin.
- Rotate it about the origin.
- Finally, translate the center of rotation back where it belonged.