ensureStableDimensions(filter);
step = factory.createPassThroughTransform(0, step, sourceDim-lowerDim);
toTarget = factory.createConcatenatedTransform(step, toTarget);
}
if (upperDim != sourceDim) {
filter.clear();
filter.addSourceDimensionRange(upperDim, sourceDim);
MathTransform step = filter.separate(toSource);
ensureStableDimensions(filter);
step = factory.createPassThroughTransform(upperDim, step, 0);
toTarget = factory.createConcatenatedTransform(toTarget, step);