Currently I'm making a voxel survival game. About a month ago I embarked on procedurally generating terrain using Perlin noise. I understand how to use and apply it for the most part. However I do not understand how to vary terrain structure. Let me say that in a way you probably can understand because "me no grammar good".
By changing frequency and amplitude I know I can change the resulting terrain, varying it from rolling hills to jagged peaks. However the end result will always be the same: either never ending hills or never ending mountains. I don't understand really how I would mix those two "terrain structures" together to get area's of hills and area's of mountains.