Ractr engine Built on Density Field Dynamics

One field is the light, the gravity and the clock.

Ractr is the first game engine derived from a unified theory of physics. No hand-built meshes for the world. No physics bolt-on. No baked light. The world, its gravity and its clocks all come from one field, solved on the GPU.

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01 The idea

Every engine since 1996 fakes the universe three times.

MeshWhat a thing looks like.
PhysicsHow it pushes back.
LightHow it’s lit, baked hours earlier.

Change one and you owe the other two.

Ractr keeps one number.

A scalar field — ψ, said “sigh” — has a value at every point in the world. Light bends through it, so it shapes the picture. Its slope is acceleration, so it’s the physics. Clocks slow where it’s dense, so it’s time. Nothing has to be kept in step, because there is only one thing.

02 The engine

One field. Three readings.

i Light

Light bends because the field does.

Where ψ is high, light slows and curves toward it, by Fermat’s principle. The engine traces that bend through its own solved field, and checks it against the theory to 0.10%.

n = e^ψ
ii Gravity

The slope you see is the slope you fall down.

Bodies accelerate down the gradient of the same field. There is no physics library and no rigid-body solver: gravity is read straight off the solved field, and it is measurably not inverse-square, because the halo is in it.

a = c²2 ∇ψ
iii Time

Clocks run slow where the field is dense.

Stand somewhere heavy and your clock slows. It is the same number again, read a third way. The engine checks the clock-rate ratio against DFD’s prediction and lands within 0.10%.

dτ = dtn = e^−ψ dt
iv One field

One number. Three laws. Nothing to sync.

Renderer, physics and time all derive from one density, ρ, so they cannot disagree. Change ρ anywhere — dig, build, blow a hole in a wall — and everything downstream of it follows.

∇·[μ(|∇ψ|/a_⋆) ∇ψ] = −8πGc²(ρ − ρ̄)

03 The new renderer

Same field. New light.

Ractr draws with a new renderer now, and this is the world through it. The world is still one density field. The renderer lights it by tracing rays through the world itself: soft shadows, ambient occlusion and light that bounces, with nothing baked.

Golden hourClearLive play

Every blade in this field is its own piece of geometry, grown on the GPU and moving in one wind. The sun breaks through volumetric cloud and glints off water on the horizon.

The trailer, cut from footage of the new renderer. Opens with sound.

Thornwood05:16Before dawnLive play

The moon low over the Thornwood before sunrise. Its face is NASA’s Lunar Reconnaissance Orbiter colour map, not a painted disc.
MoonriseNight, mistLive play

The moon rising behind a stand of trees, with mist in the hollow and stars overhead.
The black hole22:30Clear nightEngine frame

The black hole in the night sky, drawn with DFD’s own optics. The far side of its disc is lensed up over the shadow and back under it, and the stars behind it bend around it.
Roeford16:56Day rainLive play

A bridge slung between two chains of stone, each link taller than a house, with rain falling across it.
Roeford18:24DuskLive play

The same bridge that evening, with the moon coming up behind the chains.
The Heartwood13:42Clear dayLive play

A lake in the Heartwood at midday. The water reflects the trees standing round it.
The Heartwood14:51Day rainLive play

The same lake an hour later, when the weather turned. The cloud thickens and the light goes flat with it.
Roe Grove17:36ClearEngine camera

Low sun through the trees at Roe Grove. Every tree throws its shadow across the sand and into the water.
Thornwood08:02ClearLive play

Morning in the Thornwood. Light comes through the canopy and lands on the clearing in patches.
Thornwood08:02ClearLive play

The same morning, looking up. The clouds are volumes the light passes through, not a picture painted on a dome.
Tallow Quay08:34Day rainLive play

Rain at Tallow Quay. The cobbles and the wall are wet, and a deck of cloud rolls over the meadows.
Tallow Quay17:54DuskEngine camera

Dusk on the flats outside Tallow Quay, with heaped cloud low down and high cirrus above it.
17:24ClearEngine camera

The guards of a capital and of a castle, lined up for the camera. Every one is the same modular Frontier body, dressed piece by piece.
Wardholm17:36Zone lineEngine camera

Crossing into Wardholm. The screen fades out and the zone’s name comes up with its line of lore.
Wardholm17:36ClearEngine camera

A few seconds later, inside the zone. Its sky, light, fog and music have taken over from the last one’s.

Light that bounces
Soft shadows, ambient occlusion and bounce light are traced through the world’s own field every frame. Nothing is baked, so whatever you dig or build is lit like everything else.
Clouds with depth
Volumetric clouds move with the weather and shade the ground beneath them, and the air itself scatters light, so sunbeams show in the haze.
Water that looks back
Lakes and rivers reflect what stands around them. The sea is simulated every frame on the GPU from a real ocean-wave spectrum.
Grass, blade by blade
Grown on the GPU every frame, wherever the field says there is ground. Dig a hole and the grass in it is gone on the same frame.
Real trees
57 tree models that sway in the wind, let light through their leaves and throw dappled shade.
The night sky
The Moon wears NASA’s Lunar Reconnaissance Orbiter colour map. Stars and the Milky Way come out as the sky gets dark enough to show them.
Zones, the old way
Cross a zone line and the screen fades, the zone’s name comes up, and the sky, light, fog and music change to the new zone’s own.
People
Every townsperson and guard is a Frontier character: one modular body, dressed piece by piece, so a crowd doesn’t repeat.

Every frame is the running game’s own output, cropped and never retouched. “Live play” frames were captured while playing. “Engine camera” frames come from the engine’s scripted camera with the interface switched off, apart from the zone card, which is the point of that frame.

04 Permanence

Dig anywhere. Build anything. It stays.

Dig a hole or raise a wall and you are editing the world’s density directly. Nothing is swapped for a pre-made piece, and an edit costs what the edit is, not what the world is. And every hole you dig and every wall you raise stays there, for everyone, permanently.

Filmed in the engine with its cinematic camera. Each dig and build is the same edit a player makes, scripted so the camera can watch it land. Some shots run at 1.5× speed.

05 Scale

What is actually in it.

768

Named settlements

Each with a hand-written charter: who founded it, what it trades, what went wrong there. Not a name generator — 768 pieces of writing.
362

Hand-modelled props

Carts, looms, altars, chain, barrels, bells — placed by hand and by the world-builder, never by tiling.
~700

Rooms to walk into

Real doorways, upper floors, stairs you climb. An interior is not a loading screen here.
0

Baked lights

Sun, moon and bounce light are traced through the world’s own field every frame, live, on an M3 Pro laptop. Nothing is baked.
0

Free parameters

In the theory under the engine. Nothing is tuned to look right.
1

Field

Renderer, physics and clock all derive from one density, ρ. They cannot drift out of sync.
∞

Reach of the field

Gravity and the clock reach across the whole world. They never run out.
22

Devlog posts

One per build session since April, failures included. Nothing has been taken down.

06 Proof

Verified, not asserted.

Four quantitative predictions of DFD, computed straight from the solved field and checked against closed-form answers. All four are green — and two of them show the planet’s dark halo.

G1Pass

Far-field decay

ψ(r) = 2GMc²r

Graded against Newton’s 1/r, it reads high. That excess is not error: the field falls off more slowly than 1/r, which is the halo.

residual +1.56%tolerance 5%
G2Pass

Strong-field lensing

d/ds(n t̂) = ∇n

Rays traced through the solved field against the exact nonlinear solution, in a world bent 17.5° at closest approach.

error 0.10%tolerance 10%
G3Pass

Kepler’s third law

T = 2π√r³/GM

Graded against Kepler, the orbit closes early. It is the same halo, felt as a slightly stronger pull.

residual −5.86%tolerance 15%
G4Pass

Clock rate

dτdt = e^−ψ

Two clocks at two heights tick apart by the ratio DFD predicts. Over so short a baseline the halo cancels.

error 0.10%tolerance 5%

G2 is graded against DFD’s exact strong-field answer; G1, G3 and G4 against Newton. The gates run on every build.

From the devlog Post 05

The bug that turned out to be dark matter.

The lensing gate once failed at 30.7%. There was no solver bug. The engine’s world sits in DFD’s transition regime, where μ(x) = x/(1+x) makes the field fall off more slowly than 1/r — so the planet carries an emergent dark halo. It is the same mechanism DFD uses to explain galactic rotation curves without cold dark matter, running live in a game engine — and it is still there in every gate run: G1 reads 1.56% above Newton, and G3’s orbit closes 5.86% early.

Read the post

Schematic, not data.

Field equation

∇·[ μ(|∇ψ|/a_⋆) ∇ψ ] = −(8πG/c²)(ρ − ρ̄)

Light

ds² = −c²dt²/n² + dx², n = e^ψ

Matter

a = (c²/2) ∇ψ

Clock

dτ = dt / n

07 Against the old way

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 physical density, ρ. The surfaces the renderer draws are derived from it, and so are gravity and the clock.

Physics Bolted on. A separate rigid-body engine with its own idea of the world, which disagrees with the render surface. Gravity is ∇ψ of the field solved from the same ρ. There is no second model of the world to disagree with.

Light Straight rays only. Lensing and refraction are shader fakes. Rays can bend through the solved ψ, with lensing and redshift computed from the field rather than faked in post.

Editing at scale A full refill on every edit. Multi-second hitches are common, and they scale with world size. The edit changes the world where you made it. The cost is the edit’s, not the world’s.

Stability Rigid-body stacks need warm-starting and constraint stabilisation, and still fail. The physics guarantees the field always settles. It cannot blow up.

Validation “Looks right.” Four quantitative gates against analytic predictions.

08 The antagonist

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.

Meet him in BAYNE, the game playbayne.com

09 Beta testers wanted

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.

10 Public devlog · 22 posts

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, since April.

11 Work with us

Licensing and investment

Licensing

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.

EvaluationFreeFull source, internal prototyping for up to twelve months, no commercial release.
StudioRevenue shareCommercial rights, a private branch, quarterly engineering consultation.
EnterpriseBespokePerpetual rights, a dedicated partnership, custom physics modules, roadmap influence.

Talk about licensing

Investment

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 sits 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, 22 public devlog posts since April.
Terms. Accredited investors, $50K minimum, current round open.

Request the deck Read the physics 208 pp · v3.4

One field is the light, the gravity and the clock.

Every engine since 1996 fakes the universe three times.

One field. Three readings.

Light bends because the field does.

The slope you see is the slope you fall down.

Clocks run slow where the field is dense.

One number. Three laws. Nothing to sync.

Same field. New light.

Light that bounces

Clouds with depth

Water that looks back

Grass, blade by blade

Real trees

The night sky

Zones, the old way

People