DEEP FIELDa starfield built from real stellar physics

Drag to look · W A S D to fly · hold Space to warp · hover a star

Commission a build like this

◂ The work

Field controls

Stars

Bloom

Exposure

Cruise

Palette

Spectral class switch classes off to see which stars carry the colour

A frame-time governor lowers render scale and star count together when frames run long; the readout shows what is drawn.

Chapter 11 · notes

How the field is built

Everything on screen is derived from a few numbers per star. This is the chain, and the places where we simplify.

Colour is temperature

Each star has an effective temperature, and its colour is the blackbody colour of that temperature: a piecewise fit to the Planckian locus, clamped at 40,000 K, converted to linear light and scaled so two stars of equal visual flux have equal luminance. Temperature is not a free dial. It comes from where the star sits on a Hertzsprung–Russell diagram, so luminous stars are hot and blue-white and the faint crowd is orange. The O to M chips in Controls switch classes off, so you can see which stars carry the colour.

Brightness is luminosity and distance

Positions are uniform in a periodic cube 360 pc on a side that follows the camera, so there is always sky ahead and behind. Each star has an absolute magnitude M, and its apparent magnitude is recomputed from its live distance: m = M + 5 log10(d / 10 pc). Fly toward a star and it brightens by the inverse-square law. The sample is thinned toward luminous stars; a true census would be mostly stars nobody could see.

The scope in the readout counts the stars in view by apparent magnitude and tints each bar with the average blackbody colour of the stars in it, so the hot-and-bright, cool-and-faint coupling is visible in the data. In an unlimited uniform volume the cumulative count would rise as 10^(0.6 m). Ours cannot: the cube is finite and thinned toward luminous stars, so the census peaks and then falls toward the limit, m = 13.7.

A star is a point-spread function

Each star is a Gaussian core plus a halo whose width grows with brightness. The displayed amplitude is flux^0.4, a stretch borrowed from astrophotography, so the faint field is visible without the bright stars becoming discs. Bloom is thresholded: only light above 0.55 spills, through two blur levels, so the space between stars stays black. The six diffraction spikes on the brightest stars are fixed to the frame, as on a telescope with a hexagonal mirror.

Motion is exposure

Hyperspace is speed, seen through a shutter. Each star is projected through the camera as it is now and as it was 50 ms ago, position and rotation both, and the sprite stretches between the two. At cruise the streak is a fraction of a pixel; at the full warp of 900 pc/s it is hundreds. Field of view widens from 56° toward 82° with speed, and the readout shows the live value. The opening 2.8 s is the same physics, a deceleration from warp, scripted as a function of clock time so a slow machine sees the same arrival.

The sky behind the stars

The spiral galaxy has two logarithmic arms (arm phase θ − k ln r, pitch 18.4°), a bulge, an exponential disc, dust lanes on the inner edge of each arm and pink HII knots. It is drawn face-on once into a 512² texture. Each frame, every pixel's view ray is intersected with the galaxy's plane, inclined 58°, and the texture is read at the hit point, so the foreshortening is geometry and not a squash.

The nebula is domain-warped fractal noise split into three emission species, H-alpha, [O III] and [S II], plus a dust term. A palette decides which colour each species gets. Narrowband assigns them in the spirit of the Hubble palette: S II toward red, H-alpha toward gold, O III toward blue.

The pulsar

A neutron star with two beams. We set the period to 1.4 s so the eye can follow it; real pulsars run from milliseconds to seconds. The core flashes as a beam crosses the line of sight. It lives in the same periodic cube as the stars, so you can fly past it and meet it again.

What the numbers are

The frame rate and frame time are measured between animation frames. In view is the count of drawn stars that pass the same cull the GPU applies: in front of the camera, inside the frame, brighter than the limit, shown against the number drawn. Nearest and brightest are searched over the drawn stars. Speed, yaw, pitch and field of view are camera state. Render shows the buffer format (fp16 or 8-bit) and the live render scale. A frame-time governor lowers the scale and the star count together, in steps, when frames run long; the readout always shows what is actually drawn.

Controls

Drag	Look around, with inertia
Hold, or Space	Warp
W A S D, R F	Fly, Shift to boost
Arrow keys	Look
Scroll	Thrust forward and back
Hover, or tap	Identify a star, the pulsar, the galaxy or the nebula
Flick the cursor	Throw meteors
C	Constellation lines
G · N · H · 0	Controls · notes · hide the interface · home view

With reduced motion on, the field is a still composition: no arrival, no warp, no meteors, and the pulsar holds a fixed beam. Dragging and the keys still move the camera, one step at a time.

Commission a build like this