Houdini: Installation

Requirements

Houdini 19.5 / 20.x / 21.x / 22.x (Windows / macOS / Linux builds SideFX supports for that version)
Launch your Houdini version at least once before installing, so its prefs folder exists (for example Documents/houdini21.0/)
A permanent folder for the unzipped package (not a temp Downloads extract you will delete)
Python 3 on PATH for install.bat / install.ps1 (Windows prefers the py -3 launcher; the Microsoft Store python stub alone is not enough). If you have no system Python, open Houdini Command Line Tools and run: hython scripts/install_houdini_package.py

What you download

From Download or Account → Downloads you get a ZIP such as UAL-Houdini-x.y.z.zip.

Inside you should see at least:

install.bat / install.ps1 (Windows helpers)
scripts/install_houdini_package.py
package/, python/, toolbar/, python_panels/
README.md

Houdini Pro seats unlock Fab / Megascans and related Pro features after you Connect with your UAL API key (see First run).

Choose an install method

Method	When to use
A — `install.bat` (recommended)	Most artists on Windows
B — Manual `packages/` JSON	Installer cannot find prefs, studio pipeline, or you prefer SideFX packages
C — Manual `houdini.env`	Older studio setups that still manage tools only via `houdini.env`

Use only one method. Do not set UAL in both a packages/AssetLibrary.json and houdini.env at the same time — conflicting ASSETLIB / HOUDINI_PATH values are a common “panel missing” failure.

What every method must achieve:

ASSETLIB = absolute path to your unzipped UAL folder
PYTHONPATH includes $ASSETLIB/python
HOUDINI_PATH includes $ASSETLIB (shelf, Python panel, viewer states)

A — Install with install.bat (recommended)

Download the Houdini ZIP from Download
Unzip it to a stable path you will keep (example: D:/Tools/UAL-Houdini/)
Fully quit Houdini if it is open
Double-click install.bat
(or run python scripts/install_houdini_package.py / py -3 scripts/install_houdini_package.py)
The installer writes AssetLibrary.json into each detected Houdini prefs packages folder and points ASSETLIB at your unzipped folder
Start Houdini again (a full restart — not only a new scene)
Open the panel:
- Shelf tab Asset Library → Open Asset Library, or
- Windows → Universal Asset Library

Verify

In Houdini Windows → Python Shell:

import os
print(os.environ.get("ASSETLIB"))

You should see the path to your unzipped UAL folder. If it prints None, the package is not loaded — try Method B or see Troubleshooting.

B — Manual install via packages folder (SideFX packages)

This is the modern SideFX-supported way (same end state as install.bat).

1. Find your prefs folder

import hou
print(hou.getenv("HOUDINI_USER_PREF_DIR"))

Typical Windows example:

C:/Users/<you>/Documents/houdini21.0

(OneDrive redirects are fine — use the path Houdini prints.)

2. Create the packages folder (plural)

Houdini only loads JSON packages from:

<HOUDINI_USER_PREF_DIR>/packages/

Path	Result
`…/houdini21.0/packages/AssetLibrary.json`	Loaded
`…/houdini21.0/package/AssetLibrary.json`	Ignored (missing `s`)

3. Create or edit `AssetLibrary.json`

Copy package/AssetLibrary.json from the ZIP into that packages folder, or create a new file named AssetLibrary.json with:

{
    "enable": true,
    "env": [
        {
            "ASSETLIB": "D:/Tools/UAL-Houdini"
        },
        {
            "PYTHONPATH": {
                "value": "$ASSETLIB/python",
                "method": "prepend"
            }
        }
    ],
    "hpath": [
        "$ASSETLIB"
    ]
}

Replace D:/Tools/UAL-Houdini with your unzipped folder:

Use forward slashes (/)
No trailing slash required
Paths with spaces are OK when quoted only if your JSON string is valid (the path itself needs no quotes inside the JSON string beyond normal JSON quoting)

Do not leave the ZIP template placeholder (REPLACE_WITH_…) — that will not load UAL.

4. Restart and verify

Fully quit Houdini → start again → run the ASSETLIB Python check above → open Asset Library shelf / Windows → Universal Asset Library.

C — Manual install via houdini.env (legacy)

Use this only if your studio standard is still houdini.env and you are not using Method A or B for UAL.

1. Open houdini.env

File location:

<HOUDINI_USER_PREF_DIR>/houdini.env

Same prefs folder as in Method B (Python Shell HOUDINI_USER_PREF_DIR).

If the file does not exist, create it as a plain text file named houdini.env.

2. Add these lines

Replace the path with your unzipped UAL root (forward slashes):

ASSETLIB = D:/Tools/UAL-Houdini
PYTHONPATH = $ASSETLIB/python;&
HOUDINI_PATH = $ASSETLIB;&

Notes:

The ;& keeps Houdini’s default path entries (do not delete existing HOUDINI_PATH / PYTHONPATH lines blindly — prepend UAL or merge carefully)
If HOUDINI_PATH or PYTHONPATH already exist in houdini.env, put $ASSETLIB / $ASSETLIB/python first, then ; and the previous value, ending with ;& as SideFX expects
Save as UTF-8 plain text (not a Word document)

3. Restart and verify

Fully quit Houdini → start again → confirm ASSETLIB in Python Shell → open the panel from the shelf or Windows menu.

houdini.env vs packages

	`packages/AssetLibrary.json`	`houdini.env`
SideFX recommendation	Preferred for tools / plugins	Legacy; still works
Studio-friendly	Easy one file per tool	One shared file many tools edit
Risk	Low if only UAL owns `AssetLibrary.json`	Higher — easy to break other tools’ paths
UAL support	Same as installer	Supported for install; prefer packages when possible

After install (all methods)

Open the panel — the Setup Wizard should appear on first use (or Actions → Setup Wizard…)
Choose a library folder for permanent assets (Online Downloads/ lives under this root)
Keep cache separate from the library (default style: UAL CACHE HOUDINI on the same drive — not your library folder, not OneDrive/prefs)
Pick default import target (SOP vs LOP / Stage) if asked
Optional: enable online sources; for Pro features paste your UAL API key from Account → Profile into Settings → Connect
Fab / Megascans also need Epic sign-in in Settings → Online after you are entitled

Update / reinstall

Download the newer ZIP
Unzip over your existing UAL folder or into a new folder
Re-run Method A (install.bat), or edit ASSETLIB again in Method B/C if the folder moved
Restart Houdini

Or use panel Actions → Check for Updates… when your account Updates flow is configured.

To remove package registration only (Method A/B): run uninstall.bat, or delete packages/AssetLibrary.json. For Method C, remove the three UAL lines from houdini.env. The unzipped files stay until you delete that folder.

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