Piecewise affine transformation for linking EBSD and DIC maps has unusual behaviour

[BenP123]

When linking EBSD and DIC maps with a piecewise affine transform, all the grain boundaries join up to a point at the top left corner of the map. This does not happen if using a normal affine transform

[rhysgt]

Are you plotting the GBs as lines or as pixels? Looks like you might be plotting as lines and I don't think it correctly handles what is happening outside the convex hull of homologous points.

You could try to define a homologous point on each corner of the DIC map so that the piecewise affine transform is valid for the entire DIC map.