Manual Breathing

Manual Breathing Mod — Technical Overview & Design

This mod introduces a high-fidelity, immersive, and tactile Manual Respiration System to Casualties Unknown, completely transforming the gameplay loop by requiring the player to actively manage their inhalation and exhalation cycle to maintain cellular oxygenation.

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🧬 RESPIRATION MECHANICS & LUNG SIMULATION

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Rather than treating breathing as a binary state, the mod implements an organic, physical model of the human respiratory tract:

1. The Respiratory State Model

Each conscious local player's body tracks two continuous properties:

[]Lung Volume (lungAir) : The physical volume of gas currently occupying the lungs.[/]

[]Oxygen Freshness (lungFreshness) : The concentration of fresh, absorbable oxygen vs. accumulated, stale carbon dioxide.

2. Anatomical Dead Space Simulation (Capped Freshness)

To prevent a single inhale from magically "fully charging" the respiratory system to 100% capacity from an empty state, the mod models Anatomical Dead Space (the residual volume of stale air trapped in non-exchanging airways).

During inhalation, incoming ambient air is mixed with a maximum fresh efficiency of 0. 85 instead of a perfect 1. 0:

lungFreshness_new = ((lungFreshness lungAir_prev) + (0. 85 addedAir)) / lungAir_new

This means your lungs always maintain a realistic residual mixing of gases, preventing instantaneous maximum charges and forcing a consistent ventilatory rhythm.

3. Deep Inhale Alveolar Boost (Low-Volume Efficiency)

Gas exchange is most efficient at low lung volumes where the partial pressure gradient of oxygen is steepest. The mod rewards realistic deep breathing cycles by introducing the Deep Inhale Alveolar Boost:[/]

[]Inhaling at low lung volumes (lungAir close to 0) directly adds a substantial amount of oxygen to your blood (bloodOxygen).[/]

[]Inhaling at high lung volumes (shallow breathing/panting at the top, e.g., from 0. 8 to 1. 0) provides virtually zero direct blood oxygen gain.

ΔbloodOxygen = addedAir (1. 0 - lungAir_prev)^2 32. 0

This makes shallow, rapid inhalations highly ineffective, forcing the player to fully empty their lungs (lungAir to 0. 0) before taking deep breaths to maximize oxygen absorption!

4. Metabolic Oxygen Depletion

Oxygen is constantly consumed from the lungs. The rate of depletion scales dynamically with the character's physical state:[/]

[]Baseline Consumption: It takes approximately 22 seconds of breath-holding to fully deplete oxygen under quiet conditions.[/]

[]Cardiovascular Scale: High heart rate (body.respiratoryRate) increases oxygen consumption.[/]

[]Exertion Scale: Low stamina (body.stamina) indicates high fatigue, compounding oxygen consumption up to 2. 2x faster.

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🫁 VENTILATION RATE RISKS (NEW PHYSIOLOGY)

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The mod features a sophisticated, real-time Ventilation Rate and Rhythm Tracker that monitors the duration and frequency of your breathing phases. Deviations from a steady, natural cycle introduce severe physiological and visual penalties.

1. Hyperventilation (Breathing Too Fast)

Triggered by rapid, shallow tapping (breathing phase duration less than 0. 85s), which simulates hypocapnia (extreme depletion of blood carbon dioxide leading to respiratory alkalosis):[/]

[]Lightheadedness & Drowsiness: Your consciousness (body.consciousness) is continuously drained. If it falls below 30%, you pass out.[/]

[]Dizziness Camera Sway: The camera sways gently in a circular sinusoidal motion, mimicking a spinning head.[/]

[]Muscle Twitches & Jitter: Under extreme hyperventilation (level > 50%), the player experiences high-frequency tremors (muscles spasming due to alkalosis), making the camera shake rapidly.[/]

[]Staggering Slowdown: Lightheadedness saps coordination, slowing down character movement speed up to 36%.[/]

[*]Peripheral Glare Vignette: A vibrant, flickering white-blue gl