# Shader: rendinst_simple_emissive

## Overview

A simple emissive shader primarily used for basic assets such as light bulbs,
spotlights, etc. It can also be applied using an emissive mask.

### Parameters

- `script:t="emission_only_at_night=1"` – Controls emission visibility during
  nighttime only.
  - `1`: Enabled
  - `0`: Disabled

  ```{note}
  This parameter works in [*Asset
  Viewer*](../../dagor-tools/asset-viewer/asset-viewer/asset_viewer.md) also
  (setting the environment to nighttime will trigger the emission).
  ```

  ```{important}
  Always set this parameter unless emission is required at all times (e.g., for
  skyscraper lights, car headlights, etc.).
  ```

- `script:t="emission_fadeout=1000,5000,0,0"` – Controls the fade-out of the
  emission (if needed). The first two components are functional:
  - **Start** of the fade-out.
  - **End** of the fade-out.
  - The 3rd and 4th components must be included but are not used.

- `script:t="emission_strength=1"` – Specifies the strength of the emission.
  Values range from `0` to potentially infinity. A value of `1` is usually
  sufficient as the maximum.

- `script:t="emission_color=0.94,1,0,0"` – Defines the emission color in RGB,
  with conversion as follows:
  - 0 RGB = `0` in the shader
  - 255 RGB = `1` in the shader

## Functionality

### Standard Operation

The shader works based on an emissive mask located in the alpha channel of the
diffuse texture:

- **Black** – No emission
- **Lighter than black** – Emits with the intensity of white
- **Albedo color** – The emission color matches the albedo

### Separate Emission Mask

If necessary, a separate emission mask can be applied, and the shader will
automatically use it. The mask is connected in the 6th texture slot (counting
starts from 0, so in *3ds Max*, this would be the 5th slot).

A separate emission mask is typically required when procedural painting is used
on the asset, where white represents paintable areas. A conflict can arise
between the paint and emissive maps, causing areas meant to emit light to be
painted instead, and vice versa.

<img src="_images/rendinst_simple_emissive_01.jpg" width="50%" align="center" class="bg-primary">

<br>

### Object Painting in War Thunder

Not yet implemented, but this is precisely why the separate emissive mask
functionality was prepared. The idea is for a single shader to both paint and
emit light on objects – such as buildings on aircraft.

**Operation principle**:

- If only the diffuse and normal maps are connected, the shader functions as a
  standard emissive shader.
- If a separate emissive mask is connected, the shader can paint based on the
  diffuse alpha as if it were a paint mask (like the standard
  [simple_aces/rendinst_simple](./dng-shaders/rendinst_simple.md) shader in *War
  Thunder*).

```{seealso}
Painting parameters are standard for *War Thunder*, see [Procedural Rendinst
Painting](../about-assets/procedural-rendinst-painting/procedural_rendinst_painting.md).
```