// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Find an intercept for a moving target
// Not compiled or tested in-world
// Setup: Place in a spare owned prim. Set relative TARGET_POSITION, TARGET_VELOCITY and positive CHASER_SPEED. Touch for owner-only output.
// Stop / restore: Remove/disable. The script calculates only; no scene properties change.
// Notes: Uses supplied vectors only; no avatar tracking. Assumes straight constant velocity and no obstacles.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Planning only.
vector TARGET_POSITION=<12.0,4.0,0.0>;
vector TARGET_VELOCITY=<0.0,1.0,0.0>;
float CHASER_SPEED=4.0;
default
{
    touch_start(integer detectedCount)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        if(CHASER_SPEED<=0.0)
        {
            llOwnerSay("Positive speed required.");
            return;
        }
        float a=TARGET_VELOCITY*TARGET_VELOCITY-CHASER_SPEED*CHASER_SPEED;
        float b=2.0*(TARGET_POSITION*TARGET_VELOCITY);
        float c=TARGET_POSITION*TARGET_POSITION;
        float t=-1.0;
        if(llFabs(a)<0.000001)
        {
            if(llFabs(b)>0.000001)t=-c/b;
        }
        else
        {
            float d=b*b-4.0*a*c;
            if(d>=0.0)
            {
                float root=llSqrt(d);
                float t1=(-b-root)/(2.0*a);
                float t2=(-b+root)/(2.0*a);
                if(t1>0.0)t=t1;
                if(t2>0.0&&(t<0.0||t2<t))t=t2;
            }
        }
        if(t<=0.0)
        {
            llOwnerSay("No future intercept.");
            return;
        }
        llOwnerSay("Time="+(string)t+" relative intercept="+(string)(TARGET_POSITION+t*TARGET_VELOCITY));
    }
}