// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Clip a line segment to a circular boundary
// Not compiled or tested in-world
// Setup: Use a spare owned prim. Set XY endpoints A/B, CENTER and positive RADIUS. Touch for owner-only calculation output.
// Stop / restore: Remove/disable. Does not sense, collide with, or modify actual objects.
// Notes: Prints entry and exit independently; tangency can print the same point twice. Z is discarded.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Ideal geometry only.
vector A=<-5.0,1.0,0.0>;
vector B=<5.0,1.0,0.0>;
vector CENTER=ZERO_VECTOR;
float RADIUS=3.0;
default
{
    touch_start(integer detectedCount)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        vector d=B-A;
        d.z=0.0;
        vector f=A-CENTER;
        f.z=0.0;
        float a=d*d;
        if(a<0.000001||RADIUS<=0.0)
        {
            llOwnerSay("Invalid segment/radius.");
            return;
        }
        float b=2.0*(f*d);
        float c=f*f-RADIUS*RADIUS;
        float disc=b*b-4.0*a*c;
        if(disc<0.0)
        {
            llOwnerSay("No crossings.");
            return;
        }
        float root=llSqrt(disc);
        list parameters=[(-b-root)/(2.0*a),(-b+root)/(2.0*a)];
        integer found;
        integer i;
        for(i=0;i<2;++i)
        {
            float t=llList2Float(parameters,i);
            if(t>=0.0&&t<=1.0)
            {
                ++found;
                llOwnerSay("Crossing="+(string)(A+t*d));
            }
        }
        if(!found)llOwnerSay("Intersections lie outside the segment.");
    }
}