In an App designed to cut stuff up, the first thing required is a choice of “Cuttable” Materials for the player to choose from, in PowerToolsFX we included a few materials, Wood, Concrete and Metal (with varying properties that affected the tool’s feedback)
The cutting effect for materials was achieved by adding pixels to the alpha channel of the image to make “cut” areas appear where the player touched the screen.
The width of the cut area or roughness depending on material and tool used.
if the player was to outline a complete shape (and all the “cut” pixels join up) the contained area falls away.
users could also hack up famous old-masters or import their own images to layer on top of an existing material