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Let X be an affine space over a field k, and V be its associated vector space. An affine transformation is a bijection f from X onto itself that is an affine map; this means that a linear map g from V to V is well defined by the equation () = (); here, as usual, the subtraction of two points denotes the free vector from the second point to the first one, and "well-defined" means that ...
Effect of applying various 2D affine transformation matrices on a unit square. Note that the reflection matrices are special cases of the scaling matrix. Affine transformations on the 2D plane can be performed in three dimensions. Translation is done by shearing parallel to the xy plane, and rotation is performed around the z axis.
The last one (background mode 7) has a single layer that can be scaled and rotated. Two-dimensional affine transformations can produce any combination of translation, scaling, reflection, rotation, and shearing. However, many games create additional effects by setting a different transformation matrix for each scanline.
In plane geometry, a shear mapping is an affine transformation that displaces each point in a fixed direction by an amount proportional to its signed distance from a given line parallel to that direction. [1] This type of mapping is also called shear transformation, transvection, or just shearing.
The Euclidean group is a subgroup of the group of affine transformations. It has as subgroups the translational group T( n ), and the orthogonal group O( n ). Any element of E( n ) is a translation followed by an orthogonal transformation (the linear part of the isometry), in a unique way: x ↦ A ( x + b ) {\displaystyle x\mapsto A(x+b)} where ...
The similarities group S is itself a subgroup of the affine group, so every similarity is an affine transformation. One can view the Euclidean plane as the complex plane, [b] that is, as a 2-dimensional space over the reals. The 2D similarity transformations can then be expressed in terms of complex arithmetic and are given by
2D affine transformation matrix: Image title: Illustration of the effect of applying various 2D affine transformation matrices on a unit square by CMG Lee. Note that the reflection matrices are special cases of the scaling matrix. Width: 100%: Height: 100%
A specific application of linear maps is for geometric transformations, such as those performed in computer graphics, where the translation, rotation and scaling of 2D or 3D objects is performed by the use of a transformation matrix. Linear mappings also are used as a mechanism for describing change: for example in calculus correspond to ...