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.

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 transparency 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.

( TODO: example image )