The Grenadier archetype from the Monster Codex has the following ability:
At 6th level, a grenadier can detonate a bomb so that it splashes in a 20-foot cone rather than affecting a radius. The cone starts at the alchemist and extends away from her in the direction she chooses. The alchemist designates one creature in the squares affected by the cone to be the target of the bomb and makes her attack roll against that creature; all other squares in the cone take splash damage. If the alchemist has the explosive bomb discovery and throws an explosive directed blast, the cone of splash damage is 30 feet long instead of 20 feet. This ability replaces swift poisoning.
How does this interact with Smoke Bomb, which is based on the splash radius of the bomb?
When the alchemist creates a bomb, he can choose to have it create a cloud of thick smoke when it detonates. The cloud functions as fog cloud, filling an area equal to twice the bomb's splash radius for 1 round per level.
Also, does using Directed Blast provoke? You're still making a ranged attack roll to hit the target, but that would make it rather weak as you have to use it much closer to your opponents.
The Directed Blast feature changes splash radius into cone-shaped. This would work exactly the same way for Smoke Bombs, so you'd get a 20 ft cone of smoke.
Directed Blast doesn't change anything with regards to attacks of opportunity, therefor it still provokes an attack of opportunity.