This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
BumpD illustration. Created with MATLAB bump function in own August UTC Oleg Alexandrov Source code MATLAB illustration of bump function in two dimensions function main the number of data points More points means prettier picture function close to what we want but not smooth getstepfunction smooth function with small support