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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 | 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 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 emissivity.intensity texture property.
There is no need to disable dynamically emitted light by switching materials or using renderables using the Drag[en]gine. The 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.
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 solidity texture property to 0. This turns the material fully invisible not rendering it at all while still emitting light.
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 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
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. 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 color texture property with a constant emissivity.intensity for the entire material.