# Learn Houdini

Please keep the documentation for Houdini handy:

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## Interface

Please review the Houdini interface.  The **3D scene view**, the **parameter editor**, and **network editor** are where we'll work the most.

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### Hotkeys

* **Ctrl + Z** - Undo
* **Ctrl + Y** - Redo
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### Contexts and Tools

Procedural Anatomy utilizes Houdini's viewer states for manipulating the tool at various points.  This is not the same as [selection](https://www.sidefx.com/docs/houdini/basics/select.html), we have focused the tools to make them easier to use and deliver what is exactly needed in each stage.

#### Enter / Exit a tool

This is heavily used for setting up your character with Procedural Anatomy but is not implemented yet for animation transfer and the simulation rig.

Ensure your mouse is over the 3D viewport and press **enter** to start using a Procedural Anatomy tool.  The **esc** (escape) key quits the tool. &#x20;

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### Hotkeys

* **Enter** - Enter Tool
* **Escape** - Exit Tool
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Selection and visualization are two different things in Houdini, meaning you can view a node such as the **skeleton node** and modify the **model node** to see the down chain results of your edits.

### Manipulators

Manipulators are how you control or move objects in 3D space inside Houdini.  Procedural Anatomy is designed to work with an advanced feature of manipulators, enabling switching between handle alignments of object, component, and world spaces to make manipulation of the character in the viewport easier.

<figure><img src="https://content.gitbook.com/content/czlF1HeE8ElPv7Dygz6P/blobs/0QfaLODskgukTW9sPIAL/01_manipulator.gif" alt=""><figcaption><p>Selecting the sphere enables the manipulator, right clicking takes you to the Align Handle Menu.</p></figcaption></figure>

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## Hotkeys

**Y** - Cycle Translate, Rotate, Scale
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#### Change Manipulator Size&#x20;

From the top menu bar:

Edit > Preferences > Handles > Handles Scale ([link](https://www.youtube.com/watch?v=Zktk_edshB0\&ab_channel=Sachin3DVFX))