its possible to solve this graphically. i just did a quick sketch - with a 12x24 plan you'll need a 9/12 on the long side and a 5.25/12 on the short side, assuming 2' overhangs all around.

this does not put your hip over the corner post - which may or may not work structurally.

you'll also need a tension connection to keep the corners from spreading away from each other - or build a truss into the center pin idea.

with the hip offset from the corners it might make sense to do this as a common purlin system on top of primary hips and a few primary rafters.

and you'll have an odd shaped boss pin as things don't hit at right angles to each other.

and if you plan to attach a gutter board, your plumb cuts on the ends of the rafters will be different from side to side - so you can design around this with a unique end detail.