Starfield

The core idea

This is the oldest trick in computer graphics: fly a cloud of points past the camera and let perspective do the rest. Stars near the centre of the screen drift slowly; stars at the edges streak outward and accelerate as they rush past you. Nothing here is genuinely three-dimensional — it is a flat canvas — yet the brain reads depth instantly, because the one cue that matters, parallax, is exactly right.

How it works

Every star carries a 3D position $(x, y, z)$. Each frame its depth z decreases, so it flies toward the viewer. We turn that into a screen position by perspective division: scale the world coordinates by width / z and measure from the centre of the canvas.

screen_x = cx + x * (w / z)
screen_y = cy + y * (w / z)

Because z sits in the denominator, a star that is twice as far away moves half as fast and sits half as far from the centre. As z shrinks the scale factor w / z blows up, which is why near stars race outward and grow — the radius is tied to how close a star has come. When a star passes the camera (z reaches the near plane) it respawns far away, so the field never empties.

Why it reads as motion

Parallax is the whole illusion. The vanishing point is the screen centre, and the rate at which a star pulls away from it encodes its depth — the same cue you get watching fence posts blur past a car window while distant hills barely move. The Streak knob leans into this: instead of a crisp dot, it draws a line from each star's previous projection to its current one, tracing the actual path travelled in one frame. It also reduces the per-frame fade, so those lines linger as glowing warp trails rather than being wiped clean each step. Turn it down for a calm drift through space; turn it up for the jump to hyperspace.

Knobs

• Stars — how many points fill the field.
• Warp — how fast z decreases (flight speed).
• Streak — dot-to-line blend plus trail length.
• Color — star colour.