tr_init: recalibrate the default tone mapper preset

[illwieckz]

• Restore most of the range of the high lights.

When the previous preset was calibrated, the engine was missing the single-bit clamping (it was a bug). Now that the single-bit clamping is restored in lightmap input, the high light range is caped twice. This restores most of of the range of high lights on the tone mapper side.

Also we don't need anymore to use the tone mapper to workaround the bloom that was too strong when the single-but clamping was missing, since that single-bit clamping is there.

• tr_init: reduce the default bloom strength

We inherited the default bloom strength from the implementation maybe decades ago and never questioned it, so it's time to adjust it and do some visual direction on that as well.

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(old screenshots)

Here are some examples with a map not using the linear pipeline:

no tone mapping	current tone mapping preset	recalibrated tone mapping preset

This new preset has been calibrated using both the historical pipeline and the linear pipeline.

This new preset is usable with both pipelines, which was not true with the current pipeline. This allows us to start delivering maps made for the linear pipeline while keeping the ability for users to enable the tone mapper.

It's possible that such default tone mapper preset have to be recalibrated later when dynamic exposure will be merged, but for now that one fits the need.

[illwieckz]

Here are some close-up, with both the historical pipeline and the linear pipeline. We notice that with the recalibrated tone mapper preset, the dark now goes dark less quickly, and we now have much more details in the high lights.

Historical pipeline:

Scene: parpax, 1225 -2245 655 0 0

current preset	recalibrated preset

Scene: parpax, 1025 -2280 180 140 40

current preset	recalibrated preset

Linear pipeline:

Scene: parpax, 1225 -2245 655 0 0

current preset	recalibrated preset

Scene: parpax, 1025 -2280 180 140 40

current preset	recalibrated preset

[illwieckz]

That recalibrated preset also restores some specularity reflections.

Scene: parpax, 932 -2224 195 -22 70

current preset	recalibrated preset

See on the bottom half of the image, on both sides of the dark groove.

[illwieckz]

I do remembered that the current tone mapper preset was used to workaround the bloom being too strong when the single-bit clamping was missing, but that bug is fixed so we don't need anymore to use the tone mapper preset as a workaround for that bloom. So we don't need to cap that much the high lights with the tone mapper.

Having an HDR Max higher than 1 is useful to alleviate some white saturation, but 8 is really too much strong, it makes the screen gray. I tested 1.2 and it gives good enough results.

Speaking about bloom. We inherited the default bloom strength from the implementation maybe decades ago and never questioned it, so it's time to adjust it and do some visual direction on that as well.

I'm currently testing of a bunch of screens.

I tested so far:

• BenQ PD3200U, calibrated designer screen
• Thinkpad Lenovo X1 5th gen, laptop screen
• Valve Steam Deck (non-OLED), game console screen
• Nintendo Switch, game console screen

I may test more screens in the future but this selection is already providing a nice diversity.

Out of those four screens, the Steam deck screen is the only one where the white central tiles of the parpax map don't look gray with HDRMax value of 6. Having a screen that doesn't render such white tiles as grey with HDRMax 8 looks to be the exception. With HDRMax 1.2, they all look closer to what we should expect from the texture, including the Steam deck screen. I'm discussing the color of the rendered texture here, not feeling.

About the Contrast option, I noticed the render feels more pleasant with the current value of 1.6 than my proposed value of 1.2 on all screens but the designer screen, and on the designer screen, it doesn't feel unpleasant, it's just that one can feel that the contrast has been increased artificially, so that a special effect is applied. Since it's not unpleasant on the designer screen and pleasant on the other screens, we can keep that 1.6 value that was already there, so I reverted that change.

The fact the dark areas go dark faster can be contradictory with the need to have maps not being too dark, but the pleasantness of it can win over that concern, and that's the value that was already tested and was not applied on bugs when it was configured, so that looks good. Let's keep it unless we find a subtle improvement to be done.

I used the opportunity I'm doing that heavy testing for testing bloom strenght values to make it more subtle, as its strength is the common complain about it and what makes bloom hard to combine with other features. I found that 0.2 makes still it work while being subtle.

I'll do more testing and possibly with other screens, maybe adding some TV and other laptops to the bench, but that starts to be great.

I'll redo some screenshots at some point.

[illwieckz]

The reason why HDR Max 8 is good enough on the Steam Deck screen unlike other screens I tested is because that screen is very bright and then that somewhat tricks the eye to see the grey as white. We cannot expect all players to have such bright screen.

[slipher]

In the Parpax floor example I can appreciate that there is more detail in the dirty/scuffed-looking parts with the provided screenshots. Though the yellow border seems kinda over-saturated.

Something we lose with the reduced HDR max parameter is the ability to mitigate severe saturation on certain maps such as Vega and Watah. Probably some of these maps were designed for "fully clamped" overbright, i.e. r_overbrightBits 0. So an alternative way to fix such maps without rebuilding would be having a worldspawn config option to set the overbright clamping threshold. Or for cases where it affects the whole room, an adaptive exposure to decrease the brightness everywhere.

On master:

With HDR bright point 1.2 as in the current version of the PR:

This scene from Watah already looks washed out on master but is worse with decreased HDR bright point. Other examples are Watah 226 1925 923 154 42 and Vega 3354 957 199 38 3.

[slipher]

Maybe something around 2 would be a good choice for the bright point since that's the most you can get with a vanilla Q3 material (lightmap + diffuse). Values brighter than 2 can only be achieved with more complex blending or dynamic lights. Can't remember whether materials like specular maps can increase it also, or if that stuff is all clamped to [0, 1].