OnePlus announced the OnePlus 3 earlier today with a number of important improvements over last year's model. One of the more exciting is the inclusion of fast charging, which OnePlus calls Dash Charge. However, the company notes that Dash Charge is dependent on special hardware in the adapter itself. We've checked with OP, and that means you'll have to use the included hardware if you want fast charging.
According to OnePlus, this is an implementation of Oppo's VOOC, which OnePlus is the first to license and market outside of Asia. Not really surprising when you remember that OP and Oppo have the same parent company. This situation with the cable is the same as Oppo's VOOC devices, except those are microUSB. VOOC uses power control and cooling hardware in the adapter rather than the phone, thus the special hardware.
The bottom line is that fast charging works on the OnePlus 3, but it won't be as convenient as it is on other phones. For the time being, OnePlus will be the only source for Dash Charge adapters. If you get an OP3 and don't have the stock charger with you, it'll still charge just fine at normal speed on any Type-C cable. It's far from ideal, but it's better to have limited fast charging than none at all, I suppose.
- OnePlus 3