Huge lighting difference when generating envAtlas from HDR texture vs skybox cubemap

[gameatp]

Summary
I get very different lighting results when generating envAtlas in two ways:
1.generateLightingSource(hdrTexture) → good, bright, high-quality PBR lighting
2.generateLightingSource(skybox) → dark, dull, low-quality lighting

The skybox cubemap is created via EnvLighting.generateSkyboxCubemap(hdrTexture).

I noticed that in the current PlayCanvas Editor, the envAtlas is prefiltered using generateLightingSource(skybox), which produces significantly darker and less accurate lighting compared to using the original HDR texture directly.

Questions
1.Is this huge difference caused by the skybox cubemap using RGBM LDR encoding and losing HDR data/range?
2.Which method is the officially recommended way to generate lighting source and envAtlas?
3.Why is it not recommended to use the RGBM skybox cubemap as the source for prefiltering lighting?
4.Could the editor’s current approach (using skybox as input) be improved to use the original HDR texture directly for better lighting quality?
Thanks!

[gameatp]

The Editor's "Prefilter Cubemap" button internally calls generateLightingSource(skybox) to generate the envAtlas. This uses the RGBM-encoded skybox cubemap as input, which loses HDR range and results in dark/dull PBR lighting.

[slimbuck]

I believe both approaches are "correct" but generating a cubemap first results in more blur and possibly less dynamic range.

When I tested this years ago I didn't see a big difference between the two, but if you are seeing a difference then it's something we should address.

Thanks for reporting!

[gameatp]

I believe both approaches are "correct" but generating a cubemap first results in more blur and possibly less dynamic range.

When I tested this years ago I didn't see a big difference between the two, but if you are seeing a difference then it's something we should address.

Thanks for reporting!

Thanks for the response!
I’ve done multiple side-by-side tests with various HDRIs, and the lighting difference is extremely obvious and consistent:
Using generateLightingSource(hdrTexture): bright, punchy, accurate HDR PBR lighting with full dynamic range.
Using generateLightingSource(skybox) (from generateSkyboxCubemap): noticeably darker, washed-out, and loses a lot of the HDR intensity and highlights.
It feels like the RGBM encoding / LDR conversion when creating the skybox cubemap is clipping or compressing the bright HDR values, which then leads to poor prefiltering and dull lighting.
This isn’t a small difference—it’s very visible in real scenes. Would be great to see the editor support using the original HDR texture directly for envAtlas generation to preserve full HDR quality!