[Houdini] Introduction to Procedural Modelling

Introduction

I will show how to create a simple 3D model with Houdini, 3DCG software developed by Side Effects Software Inc.

You can upload the created 3D model to STYLY by exporting it as a OBJ-format file.

 

 

Required Development Environment

Windows 10

Houdini 17.5

Download Houdini

Download Houdini from SideFx.

Click ‘Get > Download’ in the menu at the top of the screen.

 

It brings up the login window.

If you don’t have an account, create it from the ‘Register’ form on the right side of the screen.

 

After logging in, the ‘Download’ screen is displayed.

Press the ‘Download’ button to start downloading the installer for Houdini.

Install Houdini

Run the Installer

Run the installer that was downloaded.

 

License Agreement

Click ‘I Agree’ to see License Agreement.

 

Select Components to Install

The next window ‘Choose Components’ will appear. Just click ‘Next’ without changing anything.

 

The Setting for Houdini Engine

Then, you will be asked if ‘Houdini Engine’ is installed.

Just click ‘Next’ as we don’t use it at this time.

 

Set the Install Location for Houdini

Set the install location for Houdini and click ‘Next’.

 

Set the ‘Start Menu Folder’

Then, it brings up a window to set the folder name that will be registered with Start Menu.

Just click ‘Next’ without changing anything.

 

The Setting to Uninstall Old Houdini Version

If the old version of Houdini has been installed, you will be asked if you want to uninstall it.

 

Click the ‘Install’ button to start the installation of Houdini. It may take a little while to install. 

 

The Installation Is Complete

When the installation is completed, the following window pops up. Click ‘Finish’ to close the installer.

 

Launch Houdini

Now, you can find ‘Houdini’ in the Windows Start Menu.

This time, click the free version of ‘Houdini Apprentice’ to launch it.

 

After launching, you will be asked if you use a free license or paid license.

This time we use the free version of ‘Houdini Apprentice’, so click ‘Next’ without changing anything.

 

It brings up EULA. Click ‘Accept’.

 

Then, the ‘non-commercial licenses were successfully installed’ message will appear. Click ‘Run’ to launch ‘Houdini Apprentice’.

‘Non-commercial licenses’ refers to the licenses for ‘Houdini Apprentice’ in this case.

 

After launching, the following screen appears.

User Interface Basics

This time we use the three windows as shown below.

Network View

You organize nodes in Network View.

In Houdini, the modelling is carried out by combining nodes.

Scene View 

The node with its display flag set to ‘ON’ is displayed in Scene View.

Note: You can toggle the display flag of a node by clicking on the right edge of the node.

Parameter View

Parameter View displays the parameters for the node selected in Network View.

 

Darken the Background Color in Scene View

In the default condition, the background color in Scene View is bright. Let’s set it to black to make models easier-to-see.

 

With the mouse pointer on Scene View, press the ‘D’ key to show ‘Display Options’.

In the Background tab, Set ‘Color Scheme’ to ‘Dark’ to darken the background in Screen View.

 

Click ‘Save as Default’ to keep the background of Screen View black for the next time. 

Houdini Basics: Create a Node in Network

I explain how to create a node in Network View here.

Show the TAB Menu

With the mouse pointer on Network View, press the Tab key or right-click to show the TAB menu.　

The TAB Menu is used to create a node.

 

Find a Node by Typing

When the TAB Menu is displayed, you can filter nodes by typing a word.

 

Then, press the Enter key once to enter the ‘node creation’ mode.

 

Press the Enter key or click the mouse to create a node at the position of the mouse pointer.

Connect Nodes

You can connect nodes by dragging the connector with the mouse.

 

Create and Connect a Node at Once

Right-clicking the connector of a node can also bring up the TAB menu.

If you create a node in this condition, you can create a node and connect it to another node at once.

 

Houdini Basics: Move Across the Levels in Network

Enter a Node

Double-click a node or press the ‘I‘ key with a node selected by the mouse to enter the node.

If you entered the ‘geo1’ node, the ‘Path’ in the upper left corner of Network View would show ‘obj/geo1’.

This ‘Path’ shows which level you are in.

 

 

Exit From a Node

Press the ‘U‘ key to return to the upper level.

That’s all for ‘Houdini Basics’.

 

Useful Operations in Network View

The following shortcuts help you to operate Network View efficiently. The important shortcuts are shown in bold.

The keyboard shortcuts are usable when you put the mouse pointer on Network View.

Description	Mouse/Keyboard operation
Pan	Drag with the middle button
Zoom	The mouse wheel
Show the whole network	Space + H
Display the TAB menu	Tab
Undo	Ctrl + Z
Redo	Shift + Ctrl + Z / Ctrl + Y
Enter the selected node	I / Enter
Exit from a node	U
Turn on the display flag on a node	R
Reverse the input connections on a node	Shift + R
Disconnect from any wires	Shake node by the mouse
Cut a connection	Y + drag with the left button
Focus the selected node	F
Jump Back	Alt + the left arrow
Jump Next	Alt + the right arrow
Layout all nodes	L
Layout the selected nodes	Shift + L
Move all inputs	Shift + drag with the left button
Move all outputs	Ctrl + drag with the left button

Create a Table

This time I will show how to create a table with Houdini.

Create an Empty Node

Create a Geometry node. 

The node is named ‘geo1‘.

 

Create a Table Top

Create a Box

Enter the geo1 node and create a Box node.

 

A Box node is created (it’s named ‘box1‘).

In Scene View, a box is displayed.

 

Resize the Box

Select the box1 node and set ‘Size X’, ‘Size Y’ and ‘Size Z’ to 2.0, 0.05, and 1.0 respectively.

It made the box into a thin board.

This completes the table top.

 

Create the Legs of the Table

Next, we are going to create the legs of the table.

 

Create a Leg

Create a Tube node and set its parameters as follows.

 

In order to display the Tube node in Scene View, you need to turn on the Display flag of the Tube node.

Click the right end of the node or select the node and press the ‘R’ key to turn on the Display flag.

 

Now, in Scene View, a bar with a square cross-section is placed so that its top face is on the XZ plane.

 

Create Points to Copy the Leg

We copy the leg four times to create the four legs of the table.

It requires four points where you copy the leg.

You can create four points by using a Grid node.

 

Firstly, create a Grid node and set its parameters as follows.

This time, the table’s size is 2.0 in X and 1.0 in Z. So I set the size in X and Y to 1.8 and 0.8 so that it fits into the inside of the table.

 

Four points have been created.

 

Copy the Leg to the Points

Copy the leg by using a ‘Copy to Points‘ node.

Connect the geometry to copy with the left connector of the ‘Copy to Points’ node and connect the point where the leg is copied with the right connector.

 

It copies the leg. Four legs are created as there are four points.

 

Merge the Legs with the Table Top

Create a Merge node to connect ‘copytopoints1’ (the four legs) and ‘box1’ (the table top).

 

 

Shift the Position in the Y Direction

Currently, the table legs extend through the ground (the XZ plane).

To correct it, shift the object in the Y direction by using a Transform node.

As the length of each leg is 1.0 this time, set 1.0 for the Y component of ‘Translate’ in the Transform node.

 

The position of the table has been shifted by +1.0 in the Y direction, so it’s on the ground now.

Congratulations. The table is now completed.

 

OBJ Export

You can upload the 3D table model created above to STYLY by exporting it as an OBJ file.

 

You can export a 3D model as an OBJ file by using a ROP Geometry node.

 

Enter the output path of the OBJ file in the ROP Geometry node (For the extension, you need to type ‘.obj’ manually).

Click ‘Save to Disk’ in the top left corner to export the OBJ file to the file path specified.

The 3D model is completed now.

 

Note: Houdini Apprentice Cannot Export FBX

The free version of Houdini Apprentice cannot export a 3D model as FBX.

To export an FBX file, you need a paid licence of Houdini.

The cheapest option, Houdini Indie, costs about 30,000 JPY for the annual subscription.

(As of May 2019)

 

In addition, you also need a paid license to create VAT (Vertex Animation Texture) etc.

Upload to STYLY

You can upload an OBJ file from Unity to STYLY.

 

How to upload an asset from Unity to STYLY

 

Note: The Setting for Houdini’s UI

Adjust the Icon Size of UI

Depending on the resolution of the monitor, you would find the UI’s icons at the top of the screen too large.

In that case, you can adjust the icon size.

 

Select ‘Edit > Preferences > General User Interface’ in the top menu.

 

You can see the size of icons changing when you change ‘Icon Size and Layout’ or ‘Playbar UI’.　

Press ‘Accept’ and then restart Houdini to apply the icon size you set to the UI.

 

UI Settings Are Saved in ui.pref

In the case of Windows10, the settings are saved in the following file.

C:\Users\{USERNAME}\Documents\houdini17.5\ui.pref

You can directly edit ‘ui.pref’ to change the size of UI.