OptiZomb Build 41

This is an unofficial, unauthorized patch. OptiZomb is not affiliated with, endorsed by, or supported by The Indie Stone.

This software modifies core game behavior. Bugs are very likely. Crashes, save corruption, and unexpected behavior may occur. Back up your saves. The author is not responsible for any data loss or damage.

Use at your own risk.

Project Zomboid wasn't built to handle massive hordes. The rendering code hammers the GPU with thousands of redundant calls per frame, and almost everything runs on a single CPU core. OptiZomb fixes the rendering side first, with multithreaded simulation coming later.

What It Does

20 client-only optimizations you can toggle on or off. Safe on any vanilla server.

Removes thousands of GPU sync stalls left over from development
Caches shader, texture, and model binds so the game stops re-doing work per zombie
Packs all zombie bone data into one GPU buffer instead of thousands of individual uploads
Caches object type checks so walls, doors, and windows aren't re-identified every frame
Merges draw calls that use the same texture atlas
Cleans up the floor rendering path (8 CPU-side fixes)
Caches floor rendering between frames when nothing has changed
Skips offscreen blood splats and caches color lookups
Batches shadow draws by texture and simplifies distant shadows
Indexes item containers so searches are instant instead of scanning every item
Sorts and ranks zombies by distance, then scales quality accordingly
Skips fine bone detail (fingers, toes) on distant zombies
Caches wall transparency checks so they only recompute when you move
Skips fog rows at distance where you can't tell the difference
Throttles AI and physics for distant zombies

Full technical breakdown →

Performance

Scenario	Vanilla	OptiZomb Lite
510 zombies (vanilla cap)	~10-15 FPS	~25-35 FPS
1,000 zombies	N/A (culled at 510)	~10-20 FPS
2,000+ zombies	N/A (culled at 510)	~5-10 FPS

Estimates based on profiling data. Actual results depend on hardware, settings, and scene complexity. Vanilla hard-caps rendered zombies at 510.

OptiZomb Full

Spreads zombie simulation (movement, pathfinding, collision, animation) across all your CPU cores. Includes 18 thread-safety fixes for vanilla bugs. Both client and server need to run the same version.

Coming Soon

Downloads

OptiZomb Lite Build 41 only

Client-only fixes. Works on any unpatched server. Install with the one-click installer.

Download Installer

*Bugs likely, backup your saves. Not compatible with Build 42.

Source Code

The new files we wrote (all the OptiZomb*.java classes, shaders, installer, config) are available on GitHub. The patches to vanilla game files are not included since those contain decompiled Indie Stone code. The installer ships binary diffs (bsdiff) for those files, not the source.

4,096 Zombies

Support the Project

OptiZomb is a solo project built in spare time. If it's helped your game run better, consider throwing a few bucks on Ko-fi. It keeps development going and helps cover testing costs.

Support on Ko-fi Join the Discord