#796 – WPF Transforms Use Homogeneous Coordinates

We saw that we can perform scale and rotation transforms on points in 2D by multiplying a 2 x 2 transformation by a 2 x 1 matrix representing a point.  A translation transform, however, could not be accomplished using a 2 x 2 matrix.  Instead, we multiply a 3 x 3 matrix by a 3 x 1 matrix that represents the 2D point.

795-001

In WPF, all 2D transforms are accomplished using a 3 x 3 transformation matrix and a 3 x 1 point matrix.  The 3 x 1 matrix contains the x and y components of the point in the first two rows and a value of 1 as the third row.  This is done so that we can easily combine scale, rotate and translation transforms, since they all use matrices of the same dimensions.

In representing a 2D point using a 3 x 1 matrix, WPF is making us of homogeneous coordinates, which involves adding a third dimension, represented by the third row of the point matrix.

About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

One Response to #796 – WPF Transforms Use Homogeneous Coordinates

  1. Pingback: #803 – Specifying an Arbitrary Transform with a MatrixTransform | 2,000 Things You Should Know About WPF

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