Yet more rotation help for Haravikk

Bah, rotations continue to elude me!

Okay, this time I have a vector, it represents an offset relative to a fixed position, and I want to rotate this offset "up" or "down" (pitch) relative to the fixed position. Now, I can get this to work for basic cases, i.e when the vector offset is "in front of" (i.e in the positive x axis from) the fixed position, but it either does nothing in other positions, or rotates in a cone shape rather than a circle.

Here is the code I have so far:

rotation rot = llRotBetween(diff, ZERO_VECTOR);

// Remove rotation
diff /= rot;
                
// Apply local-rotation
if (held & CONTROL_UP) diff *= rotUpDown;
else diff /= rotUpDown;

// Re-apply rotation
diff *= rot;

In this case "diff" is the offset, and the fixed position is unknown.
rotUpDown is a 30º rotation on the Y-axis.

How do I got about calculating the correct rotation(s) I need here?

I don't know if I understand exactly what you want to do, but it sounds to me similar to a simple door script.

Applying an offset relative to a current rotation you need to multiply the current rotation to the offset rotation. *llGetRot() (or *llGetLocalRot() for childprims with llSetLocalRot())

A simple door script.

integer switch = FALSE;
vector Axis = <0.0,1.0,0.0>;
float deg = 30.0;
rotation rot;

default
{
	touch_start(integer total_number)
	{
		if (switch){
			rot = llEuler2Rot(Axis * deg * DEG_TO_RAD)*llGetLocalRot();			
			llSetLocalRot(rot);
			switch = FALSE;
		}else{
			rot = llEuler2Rot(-Axis * deg * DEG_TO_RAD)*llGetLocalRot();
			llSetLocalRot(rot);
			switch = TRUE;
		}			
	}
}