Several places in Slicer core and extensions the bottom row of the matrix is ignored (assumed to be [0 0 0 1]). Therefore, the cleanest solution would be to make the bottom row read-only in the GUI.

@Chrystel: This could be done by adding a property named PerspectiveProjectionEditable to ctkVTKAbstractMatrixWidget

See https://github.com/commontk/CTK/blob/master/Libs/Visualization/VTK/Widgets/ctkVTKAbstractMatrixWidget.h

In addition to

Q_PROPERTY(bool PerspectiveProjectionEditable READ ...)

the methods to add will be:

bool perspectiveProjectionEditable()const;
void setPerspectiveProjectionEditable(bool value);

@jcfr: I like the idea of hiding the row as described in #9650

I would prefer to have a non-editable 4-th row, as it makes clear that the matrix is a homogenous transformation. I think the property name could be more explicit, for example 'LastRowEditable'.

By showing the last row the user could also verify that the values are indeed [0 0 0 1], as expected.

Implementation is ready. Remaining tasks:

• Integrate CTK update (https://github.com/commontk/CTK/pull/871)
• Update CTK hash in Slicer
• Update Slicer (https://github.com/Slicer/Slicer/compare/master...lassoan:disable-transformation-matrix-last-row-edit?expand=1)

Fixed in Revision: 28279