RyanB explains how to use it in his answer to this question. I have followed his steps very carefully, but cannot get it to work. The material never changes. Is there any other information on this node or an example somewhere I can see?
InterpolateMaterialInstancesParameters changes values of all parameters on a given dynamic material instance in a range between the values of the same parameters on two other material instances depending on alpha input.
eg.
This node virtually allows you to create material instances, that would represent states, and interpolate all their parameters at once, instead of handling list of parameters manually.
The actual magic where material changes should be controlled by you in the material.
eg.
You create a master material M, that contains a lerp node, that lerps between two textures based on Scalar Parameter named S.
Then you create two instances of material M, Mi_a and Mi_b, and set S to 0 and 1 for instances respectively.
In your blueprint, you create and assign a dynamic material instance Mi_d to the mesh in question.
Then you use InterpolateMaterialInstanceParameters node to gradually change Mi_d from Mi_a to Mi_b.