What is the function that transitions two materials from one over to another at runtime?

The function that transitions two materials from one to another at runtime is Lerp, which stands for linear interpolation. This mathematical function allows for the gradual transition between values, meaning it can be used effectively to interpolate between two material properties such as color, transparency, or other shader parameters.

In the context of materials, Lerp can take two materials and an interpolation factor (often between 0 and 1) to smoothly blend between them. As you adjust this factor, the appearance of the material transitions incrementally from the first material to the second, creating an effect of transitioning.

The other options, while potentially related to material manipulation, do not specifically define the process of blending one material into another through interpolation. Blend may suggest combining materials, but it lacks the specificity of a defined method like Lerp. Fade typically pertains to the gradual decrease of an object's visibility, and Transition is more general and does not denote a specific interpolation method like Lerp does. Thus, Lerp is the most accurate choice for defining the process of transitioning materials at runtime.