I also came across a commercial terrain tool I wasn't aware of:
and finally just for fun here are some retro links to some information on "White Magic 1" & "White Magic 2" - the very first games I had commercially published:
This was on the Acorn Electron back in 1990, 1 whole Mhz of 8bit power and 32K of total RAM driving a 160x256 screen resolution with four colours and a tape drive!
I couldn't afford a floppy disc drive at the time so had to assemble the code to the screen memory, save the assembly source to tape then copy the machine code from the screen memory into normal memory to run it before loading the graphics from tape each time I wanted to test anything...happy days.