transformPointsForward does not support Polynomial​Transforma​tion2D

I would like to know why transformPointsForward does not support PolynomialTransformation2D as a transformation object. It is weird because transformPointsInverse does support PolynomialTransformation2D.

So the workaround is simple, instead of using:

tform = fitgeotform2d(movingPoints,fixedPoints,"polynomial",degree)
[x,y] = transformPointsForward(tform,u,v)

I used:

tform = fitgeotform2d(fixedPoints,movingPoints,"polynomial",degree)
[x,y] = transformPointsInverse(tform,u,v)

But it is still counterintuitive and increases the risk of making mistakes later in the code.

Please let me know if there is something I am overlooking or if this is really a missing functionality of the transformPointsForward function.

This is the error I am getting when using transformPointsForward:

Incorrect number or types of inputs or outputs for function transformPointsForward.

Answer 1

[Matt J]

Polynomial tforms are generally not invertible, so you can only define them in one direction. I assume fitgeotform2d always fits the inverse transform because it is the inverse, not the forward transform that is need to perform a forward imwarp() from the moving space to the fixed space.

[Juan de Jesus]

Now that I think about it, it makes sense. That is the expected behavior from the polynomial fit. Thank you very much.

[Matt J]

You're welcome, but please Accept-click the answer if you consider your question resolved.