Vitamin RDA % is computed slightly incorrectly

[nornagon]

Describe the bug

For example, a hamburger is set in its JSON to have "vitamins": [ [ "calcium", 57 ], ... ], which appears to be intended to correspond to 57% of RDA. However, in-game it is shown as 56%. This seems to also affect the computed vitamin mass, which is listed as 563 µg instead of 570 µg which would be 57% of the 1000 mg RDA.

Attach save file

N/A

Steps to reproduce

1. Open spawn item menu and find the hamburger

Expected behavior

Calcium RDA% should be 57% at 570 µg.

Screenshots

Versions and configuration

• OS: MacOs
  • OS Version: Name: macOS; Version: 14.3; Build: 23D56;
• Game Version: cdda-experimental-2024-05-30-2137 261b61c [64-bit]
• Graphics Version: Tiles
• Game Language: System language []
• Mods loaded: [ Dark Days Ahead [dda], Disable NPC Needs [no_npc_food], Portal Storms Ignore NPCs [personal_portal_storms], Slowdown Fungal Growth [no_fungal_growth] ]

Additional context

I believe this is due to an incorrect interpretation of the vitamin's weight_per_unit.

vitamin::RDA_to_default computes:

( 24_hours / rate_ ) * ( static_cast<float>( percent ) / 100.0f )

which, for [ "calcium", 57 ], gives 24 h / 15 m * ( 57 / 100 ) = 54.72

This is rounded to an int, giving 54.

then Character::vitamin_RDA reverses this lossily:

const double multiplier = vitamin_rate( vitamin ) / 1_days * 100;
return std::lround( amount * multiplier );

giving 15 m / 24 h 100 54 = 56.25, floored to 56%.

For vitamins given as integers in the JSON, they are round-tripped through this lossy conversion from %RDA to units and back, resulting in a value in-game which doesn't always match what's in the JSON.

[Karol1223]

I believe this bug predates the current RDA weight support, unless this is somehow something different entirely. I think even back in 2022 we had reports of vitamins ingame being 1-unit smaller than JSON dictated.

[github-actions[bot]]

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