RACTR
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2026-04-15 engine rendering

New Earth

A planet you can walk on. Biomes derived from latitude and noise. A sun with a real corona. A moon with phases that fall out of geometry. Build and destroy with the physics catching up live. Three hours after gates passed.

The Earth surface

The classical approach is to build a terrain mesh, texture it, light it. Ractr doesn't have meshes, so the surface appearance has to come from the world itself. Where you are on the planet decides what the ground looks like: ice caps toward the poles, oceans, forest, desert bands by latitude, rock where the land gets rough.

No textures. No mesh UVs. No terrain generation pass. You could rotate the planet and the continents would stay locked to their latitudes, because they belong to the planet, not to a texture wrapped around it.

The sun's corona

A real sun has layered atmospheric structure visible from space: a bright photosphere (the "surface"), a red chromosphere at its rim, and a diffuse corona extending several solar radii. Ractr draws all of it, and the corona subtly breathes rather than sitting statically in the sky. It costs almost nothing.

The moon

I initially rendered the moon as a single bright disc. It looked like a second sun. The fix was to treat the moon as a real lit sphere: lit by the sun, with its own highlands and dark seas, and a touch of earthshine.

Moon phases fall out of this with no extra code. If the sun is on the same side of the planet as the moon, the side facing us is in shadow — new moon. If the sun is opposite — full moon. Every angle in between gets the correct terminator because the moon is genuinely lit, not painted.

Orbital mechanics

The sun and moon don't sit still. They orbit with periods proportional to the real solar system:

Over one minute of real time, you watch about three full "lunar cycles" while the sun moves a quarter of the way across the sky. The moon passes through every phase, correctly, because the geometry is right.

Space is space

An early version rendered blue sky even from outside the atmosphere. Now the sky does what scattering really does: light that skims the atmosphere picks up blue, and light that stays in vacuum doesn't. Flying out from the Earth gives you a smooth transition from blue sky to black space with a blue halo around the planet's limb, which is what astronauts actually see. The stars come out behind it.

Build and destroy

Left click digs. Right click builds. Either way you are changing the matter in the world, and the physics catches up on its own within moments.

What makes this stable is that the theory guarantees the field always settles. Add mass, the world settles. Subtract mass, the world settles. No constraint solver, no stabilization hacks.

What makes it cool is that, in DFD, changes in the field travel at exactly c. When you dig a crater, the gravitational effect of the missing mass ripples outward at the speed of light. Causality is built into the physics itself. In the engine, it shows up as a smooth visual ripple. Physically correct and aesthetically interesting in the same frame.

The player

The player is a test particle. Gravity comes straight from the field, and the field is the same one the renderer draws.

Newton's first law — coasting when no field is present — is automatic. Newton's second law is the field's slope. Standing on the ground, walking, and landing are handled without a rigid-body solver. No bouncing, no clipping.

Jumping is an impulse along your local "up," which points away from mass, not along some world axis. If you walked to the equator you would still jump "up" relative to the planet, because the field says so.

What runs at 60 fps

On a single MacBook Pro M3. No mesh, no BVH, no physics engine, no lightmap.

What comes next

The engine is doing things that aren't easy to do in Unreal or Unity, but the world is still 40 meters wide. The next step is scale: taking this same engine to an Earth-size planet, or a solar system, at essentially the same cost per frame.

The physics is finally on the same side of the table as the engine. From here, it's all about what we build in that space.