# Working with Meshes

{% hint style="danger" %}
The following guide assumes that you are using Rhinoceros
{% endhint %}

## Setup <a href="#id-0-2-checking-tolerances" id="id-0-2-checking-tolerances"></a>

### Vertex Snap

Ensure you ha Osnap turned on at the bottom, and vertex snap turned on. Vertices are the point sub-objects of a mesh, and can only be snapped to this way.

### Checking Tolerances <a href="#id-0-2-checking-tolerances" id="id-0-2-checking-tolerances"></a>

Check your tolerances are set correctly and suitable for 3D printing. For most cases, you should the smallest 3D printable detail size / 10. For NExT Lab machines, 0.001mm is more than enough to suffice.

```
Command : Units
```

![Figure 0.2 - Check your tolerance is set correctly in your rhino file](https://blobscdn.gitbook.com/v0/b/gitbook-28427.appspot.com/o/assets%2F-LOG7zoThcXp7wN40luI%2F-LTyg6I8tN-kpug70YGg%2F-LTyjbmCvXj79T7Q20yy%2FTolerances.PNG?alt=media\&token=76074c24-bcfd-4ac9-bf9b-76beff017391)

### Brute Force Mesh Reduction <a href="#id-0-3-checking-polygon-count" id="id-0-3-checking-polygon-count"></a>

A model with too many polygons comes with several drawbacks.

* Has problems being processed by 3D printers
* Unnecessary mesh detail that will be lost to printing
* Slow to work with as it takes up lots of computing resources

&#x20;If this is the case reducing your mesh can make printing and working with the file much easier. Reducing your mesh can result in a lower resolution so a judgement call will need to be made to on how much resolution is acceptable to lose.

```
Command: Reduce Mesh
```

## Mesh Properties and Modelling

The afore-mentioned properties in Mesh 101 are represented by the mesh topology.&#x20;

The strict description of a valid mesh can be expressed as the following:

* [ ] **All edges are manifold:** Each edge belongs to 2 faces only.
  * [ ] If an edge is used by only 1 face, this means it is a ***naked edge.***
    * [ ] **All manifold edges / 0 naked edges means that the mesh is closed.**
  * [ ] If an edge is used by 3 or more faces, it is a ***non-manifold edge.***
    * [ ] A mesh can be closed yet still have non-manifold edges.
* [ ] **All faces are pointing in the same direction**
  * [ ] If some faces are pointing inwards or outwards, this means that there is no conclusive inside or outside.

### Viewing Mesh Properties

Based on these mesh properties, it would be helpful to be able to view **face direction (backfaces in Rhino), naked edges and non-manifold edges.**

1. Head into your Rhino Options, command: Options
2. From `View > Display Modes` tab, create a **copy** of the standard Rhino **Shaded** mode, or you may edit the default **Shaded** mode instead.
3. Apply the following **Backface** and Mesh Edge Settings, use bold, high-contrast colours!

![Adjust the Backface Settings to 'Single color for all backfaces'](/files/9xYRqseKw3iEP9NR4Z40)

![Under the, Shaded > Objects > Meshes menu, apply the following settings. You may adjust the colours and Edge Thickness for more prominent edges.](/files/h2d1R3ZQYhgX0rkiGzYX)

### Examples

![](/files/jRDErCQAnybZhohjCxvG)

From applying these view settings, mesh issues can be spotted immediately! Most obviously is if you see any backfaces, this means that there is usually a **hole and therefore naked edges.**

![A closed mesh can still suffer from these instances where faces cross over each other. Sometimes these are not coloured properly by Rhino.](/files/WMHARRAUX9PlgEW8kBrz)

![Another common issue is very small gaps.](/files/kcMFt11pqn5oWCNvWlTI)

## ShowEdges

`[ShowEdges]` is the quickest way to identify any mesh issues. Simply select all the objects you want to check and type in the command.

![](/files/rYu7nh4FvlmISdOHgprq)

### &#x20;<a href="#id-1-1-displaying-backfaces-naked-edges-and-non-manifold-edges" id="id-1-1-displaying-backfaces-naked-edges-and-non-manifold-edges"></a>


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