[Insight-users] Supplying a transform to the metric?

[motes motes]

I am working on a little function that given two images computes the
metric value. In this context I was wondering if the type of transform
has any influence on the metric value.

Setting up the metric typically looks something like this:

    transform->SetIdentity();
    metric->SetTransform(transform);
    metric->SetInterpolator(interpolator);
    metric->SetFixedImage(imageF);
    metric->SetMovingImage(imageM);
    metric->SetFixedImageRegion(region);

Is it true that it does not matter what type of transform is
specified? I have tried with :

  typedef itk::BSplineDeformableTransform<CoordinateRepType,
Dimension, SplineOrder>      TransformType;
  typedef itk::AffineTransform< double, Dimension>
                       AffineTransformType;

but it does not seem to change the metric value.

If the metric only needs to get the indentity transform, is it
possible to supply this without using one of the above specific
transform typedefs?