void setva(cube &c, int cx, int cy, int cz, int size, int csi)
{
    if(verts.length())                                 // since reseting is a bit slow
    {
        verts.setsize(0);
        explicitsky = skyarea = 0;
        vh.clear();
        l0.clear();
        l1.clear();
    }

    bbmin = ivec(cx+size, cy+size, cz+size);
    bbmax = ivec(cx, cy, cz);

    rendercube(c, cx, cy, cz, size, csi);

    if(verts.length())
    {
        c.va = newva(cx, cy, cz, size);
        c.va->min = bbmin;
        c.va->max = bbmax;
    }

    l0.clearidx();
    l1.clearidx();
}