Examples: Update from GammaCorrectionShader to OutputPass

[donmccurdy]

No particular hurry, but if this is something we're interested in, I can make the same changes to the remaining examples. Would also be fine with updating usage but leaving GammaCorrectionShader un-deprecated. OutputPass is a very nice usability and performance improvement, @Mugen87. 👍

Related issue:

• Examples: Introduce OutputPass. #26102

[WestLangley]

There is a problem with OutputPass that should be fixed.

The transfer function should only be applied to luminance values that have been properly tone mapped to within transfer function's input range. (Less than 1 currently).

So NoToneMapping and LinearToneMapping are problematic.

[Mugen87]

No particular hurry, but if this is something we're interested in, I can make the same changes to the remaining examples.

Great!

I would prefer to not merge the PR before the examples are updated though. The number of examples using GammaCorrectionShader is manageable and I just want to avoid deprecation warnings in the example code so close before the next release.

So NoToneMapping and LinearToneMapping are problematic.

AFAICS, this is not a problem specific to OutputPass. The previous approach also had this issue. How do you suggest to fix it?

[WestLangley]

AFAICS, this is not a problem specific to OutputPass. The previous approach also had this issue.

Correct.

How do you suggest to fix it?

Ultimately, an appropriate tone mapping function is determined by the viewing device and the viewing environment. Likewise, the OETF is device-specific.

For what to do in the mean time, I'm open to suggestions.

[donmccurdy]

More flexible tone mapping functions are well worth exploring, as is output to Display P3. Both will take some time. In the meantime, some but not all of our tone mapping functions clamp. I don't think it would be appropriate for NoToneMapping or LinearToneMapping functions to clamp. We could do so before or after the OETF, but personally I also feel OK with just the implicit clamp imposed by the HTMLCanvas API.

Aside – "Extended" sRGB values outside [0,1] are sometimes used. I have no interest in supporting this in three.js, except to say that passing values >1 through the sRGB OETF is not always the wrong choice.

[donmccurdy]

Let's start with just updating the examples, not deprecating GammaCorrectionShader quite yet. It appears there are failures in some examples, so I'll move this to draft status.

[WestLangley]

@donmccurdy For now, I think it is appropriate to clamp LinearToneMapping. Clamping is post-exposure-control.

When we support HDR displays, this will need to be revisited.

[Mugen87]

Let's start with just updating the examples, not deprecating GammaCorrectionShader quite yet.

Totally agree! Do you think we can move with this PR forward and update at least the example that do not break? I would love to see more usage of OutputPass in the examples for r154 and more users using it in their code.

[donmccurdy]

@Mugen87 updated, thanks!