How to control Fire burning across object
I've been learning and practicing how to create fires, watching a lot of tutorials and whatnot. So at this point, I've successfully created a fire that emits from an object for example, but I was wondering how I can make a fire that can interact with an object.
Like let's say I have a doorframe, just a really simple model, rectangles extruded and whatnot. With the knowledge that I have so far, all I can do is make the entire doorframe model act as the emitter so when the animation starts, the entire doorframe lights up at once. But say I wanted the fire to start at the bottom of the doorframe, which would theoretically be made of "wood", and then ignite at the bottom and burn its way up to the top. How could I control the fire to do that?
I've been suggested to use a texture for the emitter but I'm not sure exactly what that means, and there doesn't seem to be too many resources addressing this particular aspect of fluids.