Primal Needs is a perfect modification for all the fans of increasing the game's immersion - this mod adds to the game the mechanics of thirst, hunger, fatigue, and the necessity to use the bathroom (or rather bushes).
Of course, all the aforementioned needs have to be satisfied. Otherwise, Geralt will face the negative results of starvation, exhaustion, or urinary retention... For example - the procumbent Witcher is unable to dodge or block the enemy blows, and the unattended level of hydration might lead to the complete lack of endurance regeneration. Also, the author has put some effort to implement a bit of realism - food has various effects, which depend on its type. For example, by eating sweets results in an immediate but temporary increase of energy. In turn, the effect of fully-fledged meals last for a much longer time.
Moreover, this mod introduces several new animations of drinking, eating, as well as emptying the bladder and bowels. Interestingly enough, the last two are unacceptable in public places, so if you do this e.g. in a city, the guards might attack you.
This mod can be installed manually by copying all the contents of the extracted archive into the game's main folder. After copying the files, you also have to:
1. Open the input.xml file with Notepad. To locate the file, you have to navigate from the game's main folder to: bin\config\r4game\user_config_matrix\pc.
2. Next, right over the line <!-- [BASE_CharacterMovement] --> you have to paste the following:
<Var builder="Input" id="PNToggleHud" displayName="PNToggleHud" displayType="INPUTPC" actions="PNToggleHud" />
<Var builder="Input" id="PNPee" displayName="PN_input_Pee" displayType="INPUTPC" actions="PNPee" />
<Var builder="Input" id="PNPoop" displayName="PN_input_Poop" displayType="INPUTPC" actions="PNPoop" />
3. Another file that needs to be edited is the input.setting, located in My Documents\Witcher 3. Open the file with Notepad.
4. At the top of the file paste the following:
5. Finally, save the changes and close the edited files.