# Group Modify

- Type
- Scope
- Tolerance
- View

Change here the numerical tolerances used to calculate a polytope group (or list of groups, previously selected with Group->Select, when Global is pressed). Parameters for empty entries or Local choices remain unchanged. Values too large may result in numerical inaccuracies.

### Visible

When the mix product of four vertices (defining a face and a new vertex), is larger than Visible the face is visible from the vertex and must be replaced. Increasing Visible may reduce face reconstruction, but may result in numerical inaccuracies. The whole calculation is very sensitive to this parameter, so it should be handled carefully. Currently the maximum allowed value is 1.0E-5.

For complex systems, where different faces have almost the same orientation, forming curved surfaces, setting Visible to 0 might eliminate numerical errors.

### Coplanar

The initial triangle faces are merged when the mix product of four vertices (belonging to both faces) is smaller than Coplanar. Increasing Coplanar promotes face merging, but may result in numerical inaccuracies. Currently the maximum allowed value is 1.0E-1.

Setting Coplanar to 0 disables face merging, so all faces will be triangles.
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