// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Distance across a spherical world
// Not compiled or tested in-world
// Setup: Place in a spare prim. Set RADIUS and both latitude/longitude pairs in degrees. Owner touch prints results without altering the scene.
// Stop / restore: Disable or remove. No prim properties are changed.
// Notes: Uses the haversine formula with clamping. This is a model-sphere tool; it does not query real-world geolocation.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Owner-only calculation.
float RADIUS=10.0;
float LAT1=10.0;
float LON1=20.0;
float LAT2=35.0;
float LON2=75.0;
default
{
    touch_start(integer detectedCount)
    {
        if (llDetectedKey(0)!=llGetOwner()) return;
        if(RADIUS<=0.0||llFabs(LAT1)>90.0||llFabs(LAT2)>90.0)
        {
            llOwnerSay("Invalid radius/latitude.");
            return;
        }
        float p1=LAT1*DEG_TO_RAD;
        float p2=LAT2*DEG_TO_RAD;
        float dp=(LAT2-LAT1)*DEG_TO_RAD;
        float dl=(LON2-LON1)*DEG_TO_RAD;
        float h=llPow(llSin(dp*0.5),2.0)+llCos(p1)*llCos(p2)*llPow(llSin(dl*0.5),2.0);
        if(h<0.0)h=0.0;
        if(h>1.0)h=1.0;
        llOwnerSay("Surface arc="+(string)(2.0*RADIUS*llAtan2(llSqrt(h),llSqrt(1.0-h))));
    }
}