Truncate Vertex

png png png

png

The Truncate Vertex tool looks like this Tool and is located on the Modify Tab of the Toolbar. Click the Truncate Vertex button. The value field appears on the modify tab. Enter a truncation value [d]. Geodesica prompts you to pick a primal vertex Vp.

The pop-up choice has the following options:
Hub Normal Planar
Edge Planar
Edge Non-Planar

NOTE: the ALT key modifier (Planar) option of previous releases has been dropped in favour of the new menu (Geodesica-SFX-0-9-9-9n).

Hub Normal Planar (Geodesica-SFX-0-9-9-9n)

A plane perpendicular to the hub normal is constructed at distance d down the hub normal. For each edge in the orbit of Vp, a new vertex is inserted at the intersection of the plane. The truncation face is formed where the vertex edges intersect this plane.

png

Edge Planar

A plane perpendicular to the hub normal is contructed at location Ip of the edge that has smallest hub normal angle. For each edge in the orbit of Vp, a new vertex is inserted at the intersection of the plane. The truncation face is formed where the vertex edges intersect this plane. In the development version, the user can specify to use either the shortest or longest edge when generating the intersection plane.

png

When using the option Edge (Planar), the required distance d down the edge from Vp to Ip is much larger than the corresponding distance d down the hub normal to the plane. For example, if an intersection plane is formed at 5 inches from Vp along the edge, the corresponding distance down the Hub Normal to this plane may only be 0.75 inches. Be sure to enter a small value for d when using the option Hub Normal (Planar), and a larger value for d when using Edge (Planar).

Edge Non-Planar

For each edge in the orbit of Vp, a new vertex is inserted at distance d from Vp. This option shortens all edges in the vertex orbit Vp by the specified distance d. But the resultant face is not necessarily co-planar.

Use this option when you want the prism’s radial edge lengths to be the same; in this instance planar faces are only formed where a truncated vetex is surrounded by identical faces.

The new vertices are connected to form a ‘prism’ with Vp at the apex. The prism is removed and the new face replaces Vp.

Modifier Keys

CONTROL

The resultant prism is not removed.

SHIFT

The operation is applied to all vertices in the lattice.

gif

NOTE: The dual is regenerated automatically.

png

Truncations are grouped (eg hide)

When performing truncation at a vertex, the vertex will be ignored if:

   1. The vertex is on a truncation plane.
   2. The vertex is flagged as false for centroid calculation.
   3. The number of edges at the vertex is less than 3.