What is the color space of the environment texture of AREnvironmentProbeAnchor?

Question

The documentation says the pixel format of the environmentTexture in an AREnvironmentProbeAnchor is bgra8Unorm_srgb.

https://developer.apple.com/documentation/arkit/arenvironmentprobeanchor/2977511-environmenttexture

However, when I inspect the pixelFormat property of the MTLTexture it says it's rgba16Float.

I'm trying to read the texture out as a PNG, and because it's a 16-bit float image, I'm assuming its color space is CGColorSpace.displayP3, but I'm not 100% sure. The texture looks darker than what I expected.

Could it be that the color space is sRGB, but it's 16-bit because it's actually an HDR texture stored as linear RGB?

(Tested on iPhone 12, iOS 15)

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Posted by

endavid

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Answer 1

It looks like the color space is CGColorSpace.linearSRGB. It's an HDR image, according to the paper we found:

https://machinelearning.apple.com/research/hdr-environment-map-estimation

outputs a completed environment map that is higher dynamic range (HDR, 16 bit channel)

I've updated the color space, saved it as PNG, and the output looks fine.

I'm assuming when ARKit2 was out, the environment textures were 8-bit at the time, but they've been upgraded since.

Posted by

endavid

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Answer 2

It looks like the color space is CGColorSpace.linearSRGB. It's an HDR image, according to the paper we found:

https://machinelearning.apple.com/research/hdr-environment-map-estimation

outputs a completed environment map that is higher dynamic range (HDR, 16 bit channel)

I've updated the color space, saved it as PNG, and the output looks fine.

I'm assuming when ARKit2 was out, the environment textures were 8-bit at the time, but they've been upgraded since.

Posted by

endavid

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Answer 3

Yes, by default the environment map is HDR.

Note that if you do want LDR environment textures for some reason, you can set wantsHDREnvironmentTextures to false.

Posted by

gchiste

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What is the color space of the environment texture of AREnvironmentProbeAnchor?

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