Direct ping is a PingPlotter Cloud feature that allows for better data collection on intermediate hops.
Some intermediate hops, particularly gateway routers commonly don't respond well to PingPlotter traceroute traffic, showing 70-100% packet loss. When an issue starts early in the route, and the gateway isn't responding properly, it can obfuscate the issue, with data leading you to believe that an issue is at a hop later in the route.
PingPlotter Cloud will automatically analyze your trace data, and attempt to detect gateway routers that are not properly responding to PingPlotter traceroute traffic, and put that hop into Direct Ping mode, this will directly ping the hop, which should collect better data, so you can pinpoint problems correctly when they occur. If it is detected that the intermediate hop has started responding to traceroute packets properly again, Direct Ping mode will be automatically disabled. You may also right click on a hop to toggle the Direct Ping mode manually, for any given hop. Direct Ping mode collects extra data, similar to the amount of data collected by a second trace directly to the IP, in final hop only mode. With Direct Ping enabled, as long as the host is participating in the route, that hop will be showing data sourced via a direct target, if the route changes and the host is no longer participating, the host will disappear from the route, as usual in PingPlotter.
Note: Direct Ping mode is not always the correct thing to use when seeing high packet loss on a hop. In particular as the hop number increases it is more "risky" that the host should be in Direct Ping mode. PingPlotter Cloud's systems weigh variables such as the Agent's gateway address and whether the IP is in the same subnet, the class of IP, whether or not the IP is actually able to be reached by direct pings, and trace data inspection to determine whether to automatically turn on (or off) Direct Ping mode.