bool Map::ClipToView(vert &start, vert &end, float &uStart, float &uEnd) {
    positionVec2 const left{-1.f/hfovMult,1};
    positionVec2 const right{1.f/hfovMult,1};

    auto q = end - start;
    auto qu = uEnd - uStart;
    auto t = cross(right, start) / cross(q, right);
    if( t > 0 && t < 1) {
        if(cross(right, start) > 0 ) {
            end = start + t * q;
            uEnd = uStart + t * qu;
        } else {
            start = start + t * q;
            uStart = uStart + t * qu;
        }
    } else if(cross(right, start) < 0 && cross(right, end) < 0) {
        return false;
    }

    t = cross(left, start) / cross(q, left);
    if( t > 0 && t < 1) {
        if(cross(left, start) > 0 ) {
            start = start + t * q;
            uStart = uStart + t * qu;
        } else {
            end = start + t * q;
            uEnd = uStart + t * qu;
        }
    } else if(cross(left, start) > 0 && cross(left, end) > 0) {
        return false;
    }
    /* ... */
}