Algodoo

You can make breakpads that actually wear out using this effect

thigs i cannot grind round and spongifieds objects

Ground surface can be concave where it contacts the grinding wheel.

it can only grind square objects?

It only works on Box shapes because they have a variable called "size", which is a matrix, such as [1, 2]. The wheel has code in it that subtracts from one of these values and therefore only works on boxes. Polygons cannot be resized because they are saved as a set of points. The wheel doesnt actually remove material, it just resizes the block. I tried it with a texture and it doesnt look right.

The effect is the sparks, not the grinding. I didnt try to make the grinding realistic.

dude i suggest taking the multiple piont and making fact for true in c++ though it would work only for sertian polygons though making mor shapes would be nice and i
hope you can improv this, beacuase this is a good idea