The Truncate Vertex tool looks like this 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. For each edge in the orbit of Vp, a new vertex is inserted at distance d from Vp. New vertices are connected to form a ‘prism’ with Vp at the apex. The prism is removed and the new face replaces Vp.
The resultant face is only guaranteed coplanar if, a) the Alt key is held down when picking a vertex (see below), or b) if all faces around the the picked vertex are identical.
Planar option. A plane perpendicular to the hub normal is contructed at location Ip of the edge that has smallest hub normal angle. 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.
CONTROLThe resultant prism is not removed.
SHIFTThe operation is applied to all vertices in the primal lattice.
- Use the Alt key option for planar faces: in this instance, the lengths of the prism’s radial edges will vary.
- Omit the Alt key when you want the lengths of the prism’s radial edges to be the same;
in this instance planar faces are only formed where a truncated vetex is surrounded by identical faces.
NOTE: The dual is regenerated automatically.
Below: The envelope was set to Egg Type 1 with an expansion in Y of 1.2. A 3V class I sphere was created using this envelope. The Truncate Vertex tool was then used with the Shift, Alt modifier keys. All cells in the egg are coplanar.
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.