contactTriangle

contactTriangle.vfl

// 接線 : https://examist.jp/mathematics/plane-figure/tyouten-setten/
function void drawContactTriangle(vector pA, pB, pC) {
    float lenA = distance(pB, pC);
    float lenB = distance(pA, pC);
    float lenC = distance(pA, pB);

    float x = (lenA + (-lenB - lenC)) / -2;
    vector contactPos0 = pA + normalize(pC - pA) * x;
    int contactPtN0 = addpoint(0, contactPos0);
    setpointgroup(0, "contactPoints", contactPtN0, 1);

    vector contactPos1 = pA + normalize(pB - pA) * x;
    int contactPtN1 = addpoint(0, contactPos1);
    setpointgroup(0, "contactPoints", contactPtN1, 1);

    vector contactPos2 = pC + normalize(pB - pC) * (lenB - x);
    int contactPtN2 = addpoint(0, contactPos2);
    setpointgroup(0, "contactPoints", contactPtN2, 1);
}