Unretouched, from a live session. The arch, the causeway and the hills are density, not geometry; the light is the field bending through them.
The first game engine derived from a new unified theory of physics.
One scalar field is the light, the gravity and the clock. No meshes for the world. No separate physics engine. No baked lighting. Every hole you dig and every wall you raise stays there, for everyone, permanently.
Every one of these is a light problem.
Sun through a broken arch. A moon behind a windmill. A torch in a ruin at midnight. In most engines those are shader tricks with a lighting artist behind them. Here they are the same equation that passes the solar-system tests of gravity, solved on a GPU sixty times a second.
The moon is an actual body at an actual phase, not a skybox decal. The windmill is a placeable — anyone can raise one, and it stays raised.
The torch is a real light casting into the ruin. Everything else you can see is starlight.
The path of light on the ground is specular reflection off a wet surface — computed, not painted.
The road is one of the old ways between settlements. The trunks are the size of towers, and you can walk to any of them.
Two bodies overhead at once, one of them ringed in light. Players look up, so the sky had to be worth it.
One tree's crown, close enough to touch. Scale is the point: these forests are metres, not props.
And you can walk into all of it.
A building here is not a façade with a door that loads somewhere else. It is partitioned into rooms, the doorways are cut through the walls, some of them carry a second floor with a stair up to it, and the things standing in them are modelled objects. These three were taken this week, with the interface switched off. None of them has been shown before.
Four rooms deep, through three doorways. The near light is a torch; the far light is the afternoon, coming in from outside.
Someone is standing in the next room, and there is a bed in the one after it. The torch is a modelled object, not a sprite.
The forge is in the room beyond and never appears in frame. All you get is what its light does to the doorway.
Be in the world before it opens.
The planet is deliberately mostly unexplored, and it stays that way until people arrive to explore it. Testers go in early, put their names on the map, and get to break things while breaking them still costs nothing. We take them in small waves, so every report gets read.
Not waiting?
The current alpha runs natively on Apple silicon Macs —
download the macOS build.
~900 MB, no installer: unzip it and open play.command. Combat, quests, building and online play are all in it, and it is an alpha in every sense.
Lord Bayne is the king who refused to end.
His agents walk into villages wearing other people's faces. Hail one and listen: its speech carries small wrongnesses, tells you learn to hear. Accuse it correctly and it unmasks on the spot, and the village pays a bounty. Accuse an innocent and you pay the blood price. Ignore an agent too long and it unmasks itself, mid-market, teeth first.
One field is doing all of it.
Ractr is built on Density Field Dynamics — a unified theory of gravity, optics and time that passes every laboratory and astronomical test of gravity performed to date, with zero free parameters. Every visual and physical system in the engine is a query against the same field.
One field, three systems
A single scalar ψ(x,t) is the refractive index, the gravitational potential and the clock rate, simultaneously. Renderer, physics and time share one GPU buffer. They cannot drift out of sync because they literally read the same data.
Light bends because space does
Rays curve through ψ by Fermat's principle. Lensing, redshift and visible time dilation near mass are emergent, not postprocess. The same equation that matches the solar-system tests renders your frame.
Edits cost what they are worth
Modify the density ρ in a region and the field re-relaxes locally over a few frames. No BVH rebuilds, no clipmap refills, no six-second stalls. Edit cost scales with edit volume, not world size — which is why every player edit can be permanent.
World size is not bounded
ψ decays as 1/r outside mass, so its analytic far-field works at any scale. A fine-grid simulation bubble follows the player and the exterior costs nothing. GPU cost is bounded; the world is not.
The physics cannot explode
The field equation's energy functional is convex, so the solver converges monotonically. No warm-starting, no Baumgarte, no constraint stabilisation. The maths guarantees stability where classical rigid-body stacks fail.
Verified, not asserted
Four quantitative physics gates — far-field decay, light deflection, Kepler orbits, clock dilation — all pass against analytic predictions on a 128³ reference grid, the hardest of them to 0.10%. The engine runs at 60–110 fps raymarched on an M3 Pro, and the whole solver fits in 903 KB of WebAssembly.
Same continuous world. Real physics under it.
| Capability | Classical SDF engine | Ractr |
|---|---|---|
| What the field is | Distance to the nearest surface. A geometric abstraction with no physical meaning. | A real physical quantity: refractive index, gravity and clock rate at once. |
| Physics | Bolted on. A separate rigid-body engine whose constraint solver disagrees with the render surface. | Emergent from the same field. Gravity is ∇ψ, sampled from the buffer the renderer already reads. |
| Light | Straight rays only. Lensing and refraction are shader fakes. | Rays curve through ψ. Lensing and redshift are real, not post-effects. |
| Editing at scale | Full clipmap refill on every edit — three to six second hitches are common, and they scale with world size. | Local reconvergence over a few frames, bounded by edit volume. The ripple visibly propagates at c. |
| World size | Bounded by procedural evaluation cost. Chunks, streaming, LOD pops. | Analytic far-field handles the exterior at zero cost. No chunking, no seams. |
| Validation | "Looks right." | Four quantitative gates against analytic predictions on a 128³ grid. |
We lost 50,000 lines of SDF engine the hard way and used it as a forcing function. The replacement is smaller, faster where it counts, and physically correct by construction.
Every build session, written up in public.
Including the failures. The bug that made every structure ever placed invisible. The castle QA found at the bottom of the sea. The screenshot tool that had been photographing the wrong buffer since day one. One post per session — that rhythm has held for four months.
- 222026-08-01The names were always promises967 named places and the world still read as procedural. The cause was one line of modular arithmetic deciding every field of every settlement — variation, but decided by nobody.
- 212026-07-27The hanging roadA brute search of 96,734 chords found exactly one sea crossing on the whole planet — with a bridge already standing on it. The fix was a re-definition, not a search.
- 202026-07-17Three kinds of lightIt has been a ray tracer since the day it was born; it was just missing three kinds of rays. By morning the moon cast shadows through the forest.
- 192026-07-12The Undersong opensFive agents' work landed one lane at a time — and the world got its first dungeon, four chambers carved straight out of the density field.
- 182026-07-11The first castle drownedThe first castle went up, then QA found it at the bottom of the sea. The law that followed makes a drowned city fail the build forever.
- 172026-07-11The planet was round all alongEight treetop reports, seven real fixes, one disease: the tree grid assumed a flat planet while the trees stood on a round one.
- 162026-07-11Look upEvery proof screenshot ever taken was aimed at the horizon. Players look up. The last treetop cutter falls to a better question, not a smarter fix.
- 152026-07-11The factory and the forestSeventeen releases in one marathon. Seven AI agents wrote a game's worth of content in parallel and the engine built it into the world wave by wave.
- 142026-07-11The world arrivesOne function had returned true since v0.8 — the entire terrain system was wired into a branch that never runs.
- 132026-07-11The camera was lyingThe screenshot tool had been photographing the wrong buffer since day one, hiding every character in the game from every screenshot ever taken.
- 122026-07-10The VeilStrangers walk into the village and some of them are not people. Hail them, hear the tells, and judge — every judgement broadcast to everyone online.
- 112026-07-10A sword made of fieldYou hold a weapon now, and it isn't a mesh. The first-person sword is raymarched by the same shader as the planet.
- 102026-07-05Hit playThe engine boots in a browser tab: 1.2 MB of WebAssembly, ψ solving on your own GPU, then you are walking.
- 092026-07-05EverQuest depth, one fieldA level curve: 12 quests across 6 NPCs, seven hunting camps, real equipment, con colours, drop tables. Twenty-four bot-verified stages.
- 082026-07-05The engine in a browser tabThe full field solver and raymarcher in 903 KB of wasm, solving ψ on your GPU when the page loads.
- 072026-07-05RACTR ONLINE: the MMO is realA real server, accounts and netcode: multiple players on one persistent planet, verified end-to-end by a 13-stage bot suite.
- 062026-07-05The regression that wasn'tOn a cold machine the regression refused to exist — but the audit found thirteen render passes where one belonged.
- 052026-07-04The first playableFrame time nearly halved. Classes, creatures, combat, XP, a quest — and the Shaper, an autonomous world-builder that keeps raising structures while you play.
- 042026-04-15A planet that actually worksProcedural continents, a real solar corona, moon phases derived from geometry, and build/destroy that reconverges ψ locally instead of rebuilding the world.
- 032026-04-15Four physics gates. All pass.Before rendering anything pretty, four quantitative predictions of DFD computed directly from the scalar field and checked against analytic values.
- 022026-04-14One field to render them allWhy a single scalar ψ(x,t) can replace the triangle mesh, the physics engine, the lightmap and the voxel grid — and be simpler and more correct at once.
- 012026-04-14The pivotNine months of SDF engine, taken out by a cleanup command. I couldn't recover it. I built something better from a physics paper instead.
License the engine
Ractr is source-available under commercial licence, structured so a studio can evaluate, build and scale without fighting the terms. Source stays private; licensees get access under NDA.
- Evaluation — free. Full source, internal prototyping up to twelve months, no commercial release.
- Studio — revenue share. Commercial rights, a private branch, quarterly engineering consultation.
- Enterprise — bespoke. Perpetual rights, dedicated partnership, custom physics modules, roadmap influence.
Back a category of one
Every decade a new substrate redefines games: meshes and rasterisation in 1996, programmable shaders in 2002, physically based rendering in 2014. The next one is a physics-native field, and the moat is at the physics layer rather than the code layer — a competitor would have to derive or licence the same theory.
- Two revenue lines — engine licensing cash-flows first; the studio compounds.
- Traction — four physics gates verified, a world of 768 settlements, four months of public devlog.
- Terms — accredited investors, $50K minimum, current round open.