Hip Rafter to Ridge

The ridge to hip rafter cut, along the axis of the ridge, shifts off the plan as the hip rises into position. Is there a way to determine, in degrees, how that angle changes? Say, for example, a hip is coming in at 45 degrees on the plan, and it rises 15 degrees......what does the 45 degrees become as it meets the ridge?

Pick up a copy of the "Timber Frame Joinery & Design Workbook" from our online store: http://st1.yahoo.com/tfguild/deswor.html
there are a couple very good articles in there describing the angles you are looking for,

or

use a good CAD 3D Modelor, (Modeler, Modellor?)

or

hire a timber frame designer (like me),

or

review "Hip and Valley Framing" and the Hawkindales on this web site at http://www.tfguild.org/tool2.html, which includes a downloadable spreadsheet for automation of your calculations.