water transparency modes r_oit=1 wboit

[j4reporting]

#895 (comment)

don't see the difference between those 3 images ?

@vsonnier, look at the base in the background, the windows of the building do appear brighter when looking through a transparent surface.
best seen here: r_oit 1 in both images, alkaline-1.2 map alk_tellus

[vsonnier]

OK I see that now, and the defect is indeed present in #895 screenshots s well. Although "false" I don't thing it is not game-breaking nor even bad : it made the glass surfaces in the back over-visible sure but I almost prefer that milky aspect with pseudo-fog lighting TBH, else the details were not that visible in this case.

WBOIT didn't have any visible impact on my GTX 1050Ti in my usual config, which is good. MBOIT (Moment-based) will be more taxing but I still think I'm going to be able to run it at acceptable speeds according to the litterature.
On the other hand, WBOIT had a big impact on the HD 630 integrated graphics, but by reducing the resolution from 2K to 1280x1024 I remained very fast.

Those 3 transparency options (normal, WBOIT, MBOIT) should be exposed in the menus is Graphics/Tranparency as Ironwail does, but simply in terms of accuracy vs. speed, something like "fast" (non OIT, for slowest GPUs), "standard" (WBOIT the default, probably) and "accurate" (for MBOIT)