Change data type of computed heightmap arrays to signed integer to avoid unsigned overflow.
Change data type of computed heightmap arrays to signed integer to avoid unsigned overflow.

Code that works with heightmaps such as filters/smooth.py will subtract two heights expecting to get a negative integer. Getting a very large positive one usually causes an error, so make sure signed int arithmetic gets used.

arruda/pymclevel,ahh2131/mchisel,ahh2131/mchisel,mcedit/pymclevel,arruda/pymclevel,mcedit/pymclevel