# Dimension radiation settings

Background and field radiation settings.

The entry ID is the **dimension ID**. For the Nether, use `data/minecraft/hbm/radiation_settings/the_nether.json`.

## Example:

```json
{
  "ambient_rad": 0.1
}
```

All seven fields are optional. Omitted `diffusivity`, `half_life_seconds`, `fog_rad`, `fog_chance` and `world_rad_effects` use the same-named [`radiation_config`](https://movblock.mov/ntm-next/26.3/wiki/game-settings/radiation_config.md) values.

## Fields

| Field | Meaning and default | Range |
| - | - | - |
| `diffusivity` (Optional) | Field-diffusion rate; global default 10. | `[0.000001, f64::MAX]` |
| `half_life_seconds` (Optional) | Field decay half-life in seconds; global default 120. | `[0.000001, f64::MAX]` |
| `fog_rad` (Optional) | Pocket radiation above which fog can appear; global default 100. | `[0, f64::MAX]` |
| `fog_chance` (Optional) | A pocket above `fog_rad` spawns fog with probability $1/\mathrm{fog\_chance}$ per second; global default 20. | `[1, f64::MAX]` |
| `world_rad_effects` (Optional) | Enables radiation decay of surface blocks; global default `true`. | |
| `ambient_rad` (Optional) | Background radiation in rad/s; default 0. | `[0, f64::MAX]` |
| `diffusivity_transport` | Turns block-dependent transport on or off; omitted, it is on when a [transport class](https://movblock.mov/ntm-next/26.3/wiki/hazards-and-radiation/block-transport.md) with a value other than 1.0 loaded. | |

## Background radiation

Background radiation is applied at exposure time and remains constant. An entity where the field is at or above zero takes whichever is higher, the field or the background. Absorbers can pull the field below zero, down to minus the background; there the entity takes the background minus that drain, reaching zero at the lowest point. Raw-field instruments show the field itself, including negative values.