Background color isn't interpreted correctly

[rawnsley]

There's a mismatch between how the background color looks in Blender and how it looks in Hubs, particularly for dark colors. I presume it's an RGB / sRGB thing, but I can't find a definitive reference for what color space Blender exports colors in.

[camelgod]

@rawnsley Is the background color still wrong with Blender Filmic after the Tone Mapping changes from 0.0.13? I think the Blender Filmic should give proper tone map now.

[rawnsley]

@rawnsley Is the background color still wrong with Blender Filmic after the Tone Mapping changes from 0.0.13? I think the Blender Filmic should give proper tone map now.

I don't think it was a tone mapping problem originally; probably a question of linear vs sRGB. I'll check next time I'm in Blender mode.

[Exairnous]

I believe that the issue is the exporter is storing the color in linear, but Hubs is reading it as sRGB. This also affects the fog color, and will affect the mirror component when it's added.

@netpro2k @keianhzo This should be a pretty easy fix, but somebody needs to decide whether it's Hubs that should be reading colors from glTF files in linear space or if the exporter should be writing out the colors as sRGB.

Edit: I don't think the issues with the recent threejs update have had any effect on this issue, but it may be better to wait until those are resolved and see if the issue is still present.

[Exairnous]

I think that's just converting it from a 0-1 range float into a hex color, so to fix it you'd need to convert the linear color to sRGB and then convert it to a hex color.

[keianhzo]

We need to do a linear to sRGB conversion here:
https://github.com/MozillaReality/hubs-blender-exporter/blob/0c593374c01506ee7fdf1963a68c5cc998c8c6fb/addons/io_hubs_addon/io/utils.py#L300
I have a fix, I'll push a PR.

I wonder if switching the property from COLOR to COLOR_GAMMA would also work, probably it would.

[Exairnous]

I tried COLOR_GAMMA after you mentioned it, but I'm pretty sure there wasn't any change.