> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FE Region by Body

## About this Block

**What it does:** Selects the FE Mesh elements whose center of mass lies within the tolerance value of the implicit body.

**Commons uses:**

* Choosing areas for defining material and elemental properties.
* Choosing elements for Boundary Conditions.

**Tips:**

* This block selects elements that are present within the FE Mesh. These elements include beams, shells, or cells (including interior cells).

* **How to decide which Entity type to choose:**
  * Choosing your entity depends on the type of elements available in the mesh.
    * Cells can only be selected on an **FE Volume Mesh**.
    * Shells can only be selected on **FE Surface Mesh** and **FE Lattice Mesh** (only if the lattice contains faces).
    * Beams can only be selected on beam-based FE Lattice Meshes.

## Example File

Download Example: [FE Region by Body](https://storage.googleapis.com/files-learn/static/ExtendedBlockDocs/selections.ntop)

![FE Region by Body](https://storage.googleapis.com/files-learn/static/ExtendedBlockDocs/fe_region_body.png)

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Select elements in an FE Mesh using an Implicit Body. Elements with their center of mass lying within a defined tolerance of the Implicit Body will be selected.

### Inputs

| Name      | Type                                                                 | Description                                                                                                                                          |
| --------- | -------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
| Mesh      | [FE Mesh](../../../../block-documentation/types/fe-mesh)             | The finite element mesh.                                                                                                                             |
| Entity    | FE Interior Region Enum                                              | The type of mesh entity to select.                                                                                                                   |
| Body      | [Implicit Body](../../../../block-documentation/types/implicit-body) | The implicit body to select with.                                                                                                                    |
| Reverse   | [Bool](../../../../block-documentation/types/bool)                   | Option to select entities outside the implicit body instead of inside.                                                                               |
| Tolerance | [Scalar](../../../../block-documentation/types/scalar)               | The tolerance for checking at the implicit body's Region. A positive value will effectively extend the region while a negative value will shrink it. |

### Outputs

| Type                                                         |
| ------------------------------------------------------------ |
| [FE Region](../../../../block-documentation/types/fe-region) |