+ res->vmin.x = a->vmin.x < b->vmin.x ? a->vmin.x : b->vmin.x;
+ res->vmax.x = a->vmax.x > b->vmax.x ? a->vmax.x : b->vmax.x;
+ res->vmin.y = a->vmin.y < b->vmin.y ? a->vmin.y : b->vmin.y;
+ res->vmax.y = a->vmax.y > b->vmax.y ? a->vmax.y : b->vmax.y;
+ res->vmin.z = a->vmin.z < b->vmin.z ? a->vmin.z : b->vmin.z;
+ res->vmax.z = a->vmax.z > b->vmax.z ? a->vmax.z : b->vmax.z;
+}