Hey Elen, could you elaborate on which two types you’re speaking of? There’s viewport AO, world AO, and an AO shader. The world and shader AO are rendered exactly the same – you’re just applying it to every object and material or one material in particular. This type of AO is called ‘additive’ because it adds brightness to everything except areas in contact with each other.
Viewport AO is somewhat opposite in that it darkens the areas of contact instead. This is the type you’d see in game engines (screen space AO), and is sometimes called ‘multiplied AO’ since it multiplies instead of adds to the color.
Neither of them are physically accurate, but sometimes they can help artistically by more clearly separating one surface from another.
