// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Offset a polyline corner by width
// Not compiled or tested in-world
// Setup: Put in a spare owned prim. Set noncollinear XY points PREV/CORNER/NEXT and signed OFFSET. Touch to print the plan privately.
// Stop / restore: Remove/disable; calculations do not alter objects.
// Notes: Positive offset is left of travel. Nearly parallel offset lines are rejected; sharp corners may require beveling.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Calculation only.
vector PREV=<0.0,0.0,0.0>;
vector CORNER=<5.0,0.0,0.0>;
vector NEXT=<7.0,4.0,0.0>;
float OFFSET=0.5;
float cross2(vector a,vector b)
{
    return a.x*b.y-a.y*b.x;
}
default
{
    touch_start(integer detectedCount)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        vector d1=CORNER-PREV;
        vector d2=NEXT-CORNER;
        d1.z=0.0;
        d2.z=0.0;
        if(llVecMag(d1)<0.000001||llVecMag(d2)<0.000001)
        {
            llOwnerSay("Repeated vertex.");
            return;
        }
        d1=llVecNorm(d1);
        d2=llVecNorm(d2);
        vector p=CORNER+OFFSET*<-d1.y,d1.x,0.0>;
        vector q=CORNER+OFFSET*<-d2.y,d2.x,0.0>;
        float den=cross2(d1,d2);
        if(llFabs(den)<0.000001)
        {
            llOwnerSay("Parallel corner; handle straight path separately.");
            return;
        }
        llOwnerSay("Offset corner="+(string)(p+d1*(cross2(q-p,d2)/den)));
    }
}