Browser-based light pollution simulator using real photometric data
Hi HN — author here. iesna.eu is a browser-based ecosystem for working with photometric data: parsing standard luminaire files (LDT/EULUMDAT, IES LM-63, Oxytech, ATLA-S001), running design calculations against EN 13201 / ANSI/IES RP-8 / CJJ 45 / IES-IDA MLO, and (the part I most want to show off here) rendering real urban scenes in Bevy with the photometric data driving actual streetlight behavior, including sky-glow contribution. The Skyglow Analysis demo loads a real LDT file into a Bevy scene (Khronos Bistro test asset). The luminaire's intensity distribution drives the streetlight rendering directly — no fudging — and the sky-glow grade updates live as you adjust the uplight percentage. Swap to a full-cutoff fixture and the sky goes from F (Severe) back to A (Excellent). You can see the difference on the buildings as well as in the sky. Stack: Rust core (eulumdat-rs and friends, ~20 crates handling photometric formats), Bevy for the 3D rendering, WASM for browser deployment. No backend; everything runs client-side. About a thousand lines of new code on top of the existing photometric library to make the Bevy integration work. Things I'd love feedback on:The atmospheric scattering model is currently single-scattering Rayleigh+Mie. Is that defensible for the use case, or should I move toward multi-scattering? The Bistro test scene works well visually but isn't a controlled environment. Anyone know of a public urban geometry asset that's more typical of real road-lighting evaluation? The CJJ 45 implementation (China's national road lighting standard) is the only one I've had to reverse-engineer from translated PDFs. If anyone has primary-source experience with it, I'd value a sanity check.Open-source on GitHub (eulumdat-rs and the related crates). Crates.io: eulumdat
FL score
out of 100
Verdict
medium confidence
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A technically impressive open-source tool for photometric simulation that solves a real niche problem, but lacks clear monetization and market validation.
The pain
The gap
Build angle
Strengths
- Technically sophisticated: Rust + Bevy + WASM is a defensible, performant stack
- Standards-compliant: Implements 4 major international standards (EN 13201, ANSI/IES RP-8, CJJ 45, IES-IDA MLO)
- Real photometric data: Uses actual LDT/IES files, not approximations
- Open-source foundation: Builds community trust and enables ecosystem integrations
- Solves a regulatory problem: Light pollution is increasingly regulated globally
- No backend required: Low operational overhead, scales infinitely
Risks
- Market size unclear: Niche audience (lighting designers, municipalities). TAM may be <$100M globally
- No monetization strategy: Open-source + free tool = unclear path to revenue
- Competing against entrenched players: AGi32, Dialux have 20+ year moats, manufacturer relationships
- Validation gaps: Author is asking for feedback on core technical choices (atmospheric model, test scenes), suggesting incomplete validation
- Regulatory adoption is slow: Even if technically superior, municipalities move slowly on new tools
- Requires domain expertise to use: Not a consumer product; needs sales + support infrastructure
- Atmospheric model may be insufficient: Single-scattering Rayleigh+Mie may not match real-world sky-glow for regulatory compliance
- Geographic fragmentation: Different standards per region (China vs. EU vs. US) = support burden
Fly Labs Method
Is the pain real, is there a gap, is it the right time, can one person build it.
Value Equation
Dream outcome and how likely it feels, against the time and effort it costs.
One-Person Business
Curiosity pull, identity fit, and a path from free value to paid for a solo creator.
Viral Frameworks
Hook strength, shareability, and how cheaply it can be tested.
Builder Lens
Evidence the problem exists, timing, defensibility, and a model that fits on a napkin.
Five lenses, one composite. How scoring works
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