What Is an IFF File?
.iff file - a container holding multiple resources that together define how an object looks and behaves.Tools
All free - all from the same GitHub repository
| Tool | What It Does | Level | Download |
|---|---|---|---|
| Transmogrifier (TMog) | Clones any game object as a new .iff - always start every mod here | 🟢 Beginner | Simlogical ↗ |
| IFF Pencil 2 | Full .iff editor - sprites, BHAV scripts and all other resources | 🟡 Intermediate | GitHub ↗ |
| Constant Contraption | Edit numeric values like price, skill gain rate, motive impact | 🟢 Beginner | GitHub ↗ |
| Career Creator 3 | Specialised editor for creating new career tracks | 🟢 Beginner | GitHub ↗ |
| Strings Scavenger | Edit text labels - object names and interaction menu text | 🟢 Beginner | GitHub ↗ |
| FARx | Extract individual .iff files from .FAR container bundles for editing | 🟡 Intermediate | GitHub ↗ |
| Simpose / Simposium | Create custom Sim poses and animation sequences | 🔴 Advanced | Awesome Expression ↗ |
Your First Mod - Changing Object Values
A beginner-friendly starting point
Open Transmogrifier
Find the object you want to modify and click Clone. This creates a safe copy to edit without touching the original game file.
Open the clone in Constant Contraption
The BCON entries list numeric values for the object. Labels will help you identify what each value controls - prices, skill rates, energy impacts etc.
Change the values you want
Edit the numbers - for example, increase a bookcase's skill gain value to make it teach skills faster, or lower a sofa's price.
Save and test
Place the cloned .iff in your Downloads\ folder, launch the game and test. If something seems off, go back and adjust.
Adding New Interactions
Intermediate - requires understanding BHAV trees
Clone your target object with TMog
Example: clone a mirror .iff to add an outfit-change interaction to it.
Open in IFF Pencil 2 and find the main BHAV
The main BHAV controls what options appear in the pie menu when a Sim clicks the object. Look for the BHAV labelled "main" or "root".
Add a new branch
Add a new interaction option to the pie menu, pointing to a new BHAV you create that performs the action (or calls an existing one from another object).
Study existing BHAVs
Look at how the dresser's outfit-change BHAV is structured to understand how to call the same routine from your mirror. The Simblr.cc community is helpful for questions.
Creating Custom Careers
Replaces an existing career - this is a Sims 1 engine limitation
GameData\Objects\ (not Downloads - it's replacing a base game file).Decide which career to replace
The Sims 1 has 10 career tracks: Business, Entertainment, Law Enforcement, Medicine, Military, Politics, Pro Athlete, Science, Slacker and Xtreme. Pick whichever one you're happy to lose - your custom career will take its slot completely. Sims already in that career will continue in it but the track will now have your custom names and values.
Open Career Creator 3 and load the career
Launch the tool and open the .iff file for the career you're replacing. Career .iff files are in your game's GameData\Objects\ folder - they're named things like career_business.iff. Loading the original gives you all the existing values to work from.
Set up the career basics
Change the career name and set the number of job levels (up to 10). Each level gets its own job title, daily wage, and work schedule. Think through the progression - entry-level jobs typically pay less and have more days worked per week.
Configure each job level
For each level, fill in the job title, salary, work days and hours, and the number of friends required for promotion. You can also set which skills are needed to advance - requiring Cooking or Charisma, for example, before a Sim can move up.
Set the carpool vehicle
Choose which vehicle picks your Sim up for work. Options correspond to vehicles available in your installed expansions. Purely visual, but worth setting to something that fits your career theme.
Save and install
Save the modified .iff file and drop it into GameData\Objects\ - not the Downloads folder. Since you're replacing a base game file, it needs to go where the original lives. Back up the original .iff first so you can restore it if needed. Launch the game and the career should appear with your new name and values in the job listings.