How to create an iso-surface along an arbitrarily oriented plane?
Sometimes one needs to create an iso-surface that is arbitrarily oriented in space,
i.e. not parallel or perpendicular to any coordinate axis. This is accomplished as follows:
1. First determine the direction cosines of the vector perpendicular
to the wanted iso-surface.
If you know three points on the plane, then it is easy to determine the
direction cosines of the vector perpendicular to the plane. Let the points
be A B C. The vector cross product of vector AB and vector BC is a vector
perpendicular to the plane containing A B and C.
2. Under Define->CustomFieldFunctions, create a customfieldfunction:
custom_field_function_0 = ax+by+cz
Here a, b, c are the direction cosines of the perpendicular vector that
you have determined in step 1. x,y,z are Grid->X-coordinate, etc.
3. Using the coordinates of one of the points A B or C, calculate the
the value of ax+by+cz.
4. Make sure that the case is initialized. Solve->Initialize->Initialize
5. Go to Surface->Iso-Surface
Select Iso-Surface of custom_field_function_0
Under 'value' type the value that you calculated in step 3. above.
Click on Create/Apply
The iso-surface is created.