Starfield Screensaver Simulator
Create a seeded starfield screensaver, tune perspective and motion, and check scene intensity against measured browser performance.{{ summaryTitle }}
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Flight director
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Introduction:
Forward motion through a starfield is a perspective illusion. Points appear to spread from a flight centre because their simulated depth shrinks over time. Nearer points move farther across the screen between frames, while distant points drift more slowly. The eye joins those different speeds into a tunnel even though every star is drawn on a flat canvas.
Several cues strengthen or weaken that impression:
- Depth separation comes from near and far motion bands plus parallax drift.
- Travel intensity comes from forward speed, warp streaks, and comet cadence.
- Composition comes from the flight centre, horizon tilt, colour, and background glow.
- Surface texture comes from star density, size, twinkle, and trail persistence.
More motion does not always make depth clearer. High speed with heavy parallax can push nearby points across the screen so quickly that the tunnel becomes noisy. Long streaks and frequent comets add a strong sense of travel but can compete with subtitles, presentation text, or a quiet room setting. A small change to one cue is often easier to judge than raising several at once.
Frame-rate targets describe requested cadence. Actual delivery depends on canvas size, device pixel density, display refresh, browser load, and other work on the device. A profile that holds 60 FPS in a small preview may need fewer visible stars at fullscreen size. That performance change is separate from the configured scene-intensity scores.
A scene seed fixes the initial pseudo-random positions, colours, phases, and comet sequence. Reapplying the same seed and settings makes comparison more repeatable, but it does not guarantee identical timing across devices because frames may arrive at different intervals.
Fast radial motion, strong tilt, flicker, and bright fullscreen contrast can be uncomfortable. Use a still preview when reduced motion is preferred, lower speed or warp when the centre feels forceful, and stop playback if the scene causes dizziness, nausea, eye strain, or distraction.
How to Use This Tool:
Build the perspective structure first, then add streaks and atmosphere before checking live delivery.
- Choose Theme and Star colours. These set the palette without changing travel, depth, or atmosphere scores.
- Set Star count, Travel speed, and Depth layers. Start near the middle of their ranges so near and far motion remain easy to compare.
- Add Warp strength and Parallax drift gradually. Use Flight director to catch aggressive travel, shallow depth, or a heavy near/far split.
- Tune twinkle, comets, centre bias, horizon tilt, nebula glow, star size, and trail fade for the intended viewing setting. Apply the edited scene so the preview uses the new snapshot.
- Start playback and compare measured FPS with the selected target of 30, 45, or 60 FPS. Repeat the check in fullscreen because the larger canvas can reduce delivery.
- Keep the same Scene seed when comparing two profiles. Reset the preview to restore the applied seed, clear active comets, and return adaptive quality to 100%.
Interpreting Results:
Flight director classifies travel, depth, and atmosphere from the configured settings. These labels describe the scene model, not astronomical realism or guaranteed viewer comfort.
- Soft travel may look nearly static; Aggressive travel is driven by high cruise load or warp above 76.
- Shallow depth means two or fewer depth bands with parallax below 25. Heavy requires depth load above 6.2 and speed above 1.6×.
- Review atmosphere appears only when absolute tilt is above 26° and comet rate is above 1.1×.
- Current delivery combines measured FPS with adaptive quality. A lower quality percentage means fewer requested stars are being drawn to protect cadence.
Judge motion from the live preview, not the configured scores alone. If measured FPS remains low or quality falls toward 60%, reduce star count, warp, comets, canvas size, or the target frame rate and test again.
Technical Details:
Each star stores horizontal and vertical coordinates around a centre plus a depth value. Perspective projection divides the horizontal and vertical coordinates by depth, so motion accelerates outward as depth approaches zero. Horizon tilt rotates the projected coordinates, while centre bias shifts the common origin.
Mechanism Core
| Stage | Mechanism | Visible effect |
|---|---|---|
| Seed scene | The seed initializes star positions, sizes, colour phases, and later comet draws. | The same applied profile starts from the same scene arrangement. |
| Assign depth | Stars cycle across 2 to 5 depth bands, each with a different forward rate. | Near and far stars separate in motion. |
| Project | Horizontal and vertical positions are divided by depth, rotated by tilt, then shifted to the flight centre. | Points spread outward and form a tunnel. |
| Advance | Depth decreases with elapsed time, speed, and band position. Stars leaving the field are reseeded. | Continuous forward travel without a fixed endpoint. |
| Draw accents | Warp extends motion streaks; twinkle changes pulse; comets follow a seeded timed cadence. | Extra speed and atmosphere cues. |
| Adapt delivery | The visible star share falls when measured FPS is below 72% of target and rises when it exceeds 95%. | Quality changes in 10-point downward or 5-point upward steps between 60% and 100%. |
Formula Core
The three director loads condense different control groups. They are repo-authored scene indices rather than physical quantities.
Cruise intensity maps cruise load 3.25 to 100%. Depth intensity maps the minimum load of 2 to 0% and the maximum declared load of 7.22 repeating to 100%. Atmosphere intensity maps a load of 95 to 100%. Each percentage is clamped to the 0% to 100% range.
Streak percentage combines speed, warp, and trail fade. It reaches 100% only when all three are at their declared maximums.
Rule Core
| Signal | Exact condition | Otherwise |
|---|---|---|
| Soft travel | Cruise load < 0.7 and comet rate < 0.25 | Balanced unless aggressive |
| Aggressive travel | Cruise load > 2.35 or warp > 76 | Balanced |
| Shallow depth | Layers ≤ 2 and parallax < 25 | Balanced unless heavy |
| Heavy depth | Depth load > 6.2 and speed > 1.6 | Balanced |
| Sparse atmosphere | Nebula glow off and twinkle < 34 | Balanced unless disorienting |
| Disorienting atmosphere | Absolute tilt > 26° and comet rate > 1.1 | Balanced |
Motion and Performance Notes:
The starfield profile stays in the browser and is not uploaded. Performance measurements are local observations, not portable benchmarks.
- Reduced-motion preference keeps the preview still and prevents normal playback.
- The browser pauses animation when the page becomes hidden and may resume it when the page returns.
- Adaptive quality never draws fewer than 96 stars, even when 60% of a small requested count would be lower.
- Colour themes and nebula glow are artistic choices; the simulation does not represent real star positions, distances, or travel physics.
- Fullscreen motion can feel stronger than the same profile in the embedded preview.
Worked Examples:
Quiet deep-space drift
Use four depth layers, 1× speed, little parallax, no warp, and a low comet rate. The flight director should remain Balanced or Soft while the scene still shows near/far separation. If it reads as Shallow, raise parallax above 24 or use more than two layers rather than adding warp.
Fullscreen warp check
Apply a high-density profile at 60 FPS, then open fullscreen and let the delivery measurement settle. If quality drops below 100%, keep the seed fixed and lower star count first. That isolates performance from composition and makes the before-and-after comparison easier to trust.