{{tag>graphic skin texture emission}}
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[[:start|Start Page]] >> [[:gamedev|Game Development with the Drag[en]gine]] >> [[gamedev:skinproperties|Skin Texture Properties]] >> [[gamedev:texturepropertylist|Texture Property Database]] >> **emissivity**
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====== Skin Texture Property: emissivity ======

Defines the emissivity.

|Excepted Data Source|3 component image|
|Data Range|0 to 1 for all components|
|Default Value|(0, 0, 0)|
|Affected Modules|Graphic|
|Linked Properties|[[gamedev:textureproperties:emissivity_intensity|emissivity.intensity]]|

====== Description ======

The **emissivity** texture property defines the light emission of the surface. Using light emission objects glow in the darkness. Emission is not affected by **[[gamedev:pbr|Physically Based Rendering]]** as it acts as a light source. This texture property defines the color of the emitted light. This allows to use an 8 bit image as the source as well as allowing to adjust the light emission strength individually using the **[[gamedev:textureproperties:emissivity_intensity|emissivity.intensity]]** texture property.

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There is no need to disable dynamically emitted light by switching materials or using **[[gamedev:renderables|renderables]]** using the Drag[en]gine. The **[[gamedev:pbr|Physically Based Rendering]]** uses high defninition range rendering. If your emitted light has an intensity of 1 or less while the object stands in the sun with over 10 intensity all around the emitted light is not going to contribute much to the illumination of the scene which is consistent with the real world. If your materials shines at night just add an emissivity texture and forget about the rest. It will just work.
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This texture property is also used for **holographic materials**, **ghosts** or other objects where typically transparency effects are used in other game engines. Transparency effects are though physically wrong for these materials. Furthermore transparency is slower than emission. In the Drag[en]gine you have to use a physically correct way to define these materials. You have to set the **[[gamedev:textureproperties:solidity|solidity]]** texture property to 0. This turns the material fully invisible not rendering it at all while still emitting light.
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The source is typically an 8 bit 3 component image with all components in the range from 0 to 1. High definition range values above 1 are possible if extrem light differences are required. Better use though the **[[gamedev:textureproperties:emissivity_intensity|emissivity.intensity]]** texture property to scale the intensity of the emitted light.

The default value for this texture property is (0, 0, 0) not emitting light at all.

====== Examples ======

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{{ :gamedev:textureproperties:emissivity.png |Vending machine at day and night with automatic lights due to the emissivity texture property}}
<WRAP centeralign>Vending machine at day and night with automatic lights due to the **emissivity** texture property. There is no need to enable or disable lights using game scripts. **[[gamedev:pbr|Physically Based Rendering]]** takes care of letting your materials emit light if it is dark. The **emissivity** texture property is set to a color image resembling the **[[gamedev:textureproperties:color|color]]** texture property with a constant **[[gamedev:textureproperties:emissivity_intensity|emissivity.intensity]]** for the entire material.</WRAP>
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