link" class="tsd-anchor-icon"><svg viewBox="0 0 24 24"><use href="../assets/icons.svg#icon-anchor"></use></svg></a></li><li class="tsd-description"><div class="tsd-comment tsd-typography"><p>This returns the gravitational field in the Y direction acting on a vertex at the given point.
By default there is no gravitational field at any location.</p>
<p>Used to define an external gravitational field at a point independent of the vertex masses.
A vertex L is acted upon by a force in the Y direction of proportio