// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Map a decal point between triangles
// Not compiled or tested in-world
// Setup: Use a spare owned prim. Set source A/B/C, target U/V/W and source point P. Touch for owner-only results.
// Stop / restore: Disable/remove. No scene properties change.
// Notes: Target need not share the source plane. Points outside the source triangle extrapolate outside the target.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT.
vector A=<0.0,0.0,0.0>;
vector B=<1.0,0.0,0.0>;
vector C=<0.0,1.0,0.0>;
vector P=<0.25,0.5,0.0>;
vector U=<3.0,4.0,2.0>;
vector V=<7.0,4.0,2.0>;
vector W=<3.0,8.0,5.0>;
default
{
    touch_start(integer detectedCount)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        vector a=B-A;
        vector b=C-A;
        vector p=P-A;
        float aa=a*a;
        float ab=a*b;
        float bb=b*b;
        float pa=p*a;
        float pb=p*b;
        float d=aa*bb-ab*ab;
        if(llFabs(d)<0.000001)
        {
            llOwnerSay("Degenerate source triangle.");
            return;
        }
        float v=(bb*pa-ab*pb)/d;
        float w=(aa*pb-ab*pa)/d;
        llOwnerSay("Mapped point="+(string)((1.0-v-w)*U+v*V+w*W));
    }
}