And found some more info, a bit wonky because of Google Translate:
PCGH: Some games with GPU PhysX support also support the rendering of effects on the CPU, at least in the representation of clothing or in the destruction physics. During the course cost performance, it works on powerful processors, at least in medium detail level quite well. Will it also be possible in The Witcher 3, represent the PhysX effects on the CPU?
Balázs Török: Yes. The default behavior of PhysX simulations such as APEX Destruction Cloth or even to render the effects on the CPU. So this will also work in The Witcher 3 without PhysX GPU. Indeed, it is for the developer even more work if he wants to calculate the effects of the GPU. GPU PhysX allows, in principle, simply increasing the level of detail. It can thus be shown, for example, more particles. But as standard uses PhysX as I said the CPU.
PCGH: So unlike, for example, the smoke in Assassins Creed 4, which can be activated only on Nvidia cards and even then requires a lot of power?
Balázs Török: The problem with the smoke presentation by APEX Turbulence is that the effect can be solely represented by the GPU. Turbulence is one of the modules, which can only be calculated on the GPU and it works - at least at this moment - only with Nvidia graphics cards. We are thinking about to implement it. But this decision is, to be honest, less on the programmer's side, but is more of a bussiness thing. And it is not an effect that necessarily results in an advantage for the feel or the immersion of the player.
