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In order to use the 'Wind' material function correctly the function states you need to reference the 'Wind Directional Source' actor. The only way to do this within the material editor and through blueprints would be to convert the vector4 to a parameter, and call this parameter through blueprints.
The documentation does state "in development" so I am unsure if this is still the case or not, but the 'Wind' function will accept a plain Vector4 with no problems. As soon as you convert the Vector4 to a Parameter, an error message appears in the stats window stating, "[SM5] Function Wind: Cannot cast from float3 to float4.
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