Use of “_MeshLight”

Credit: User BahnLand with translation by 3d-train-studio.uk.

A “_MeshLight” object is an object whose surfaces glow at night. The glow is limited to the surface area of the object. The surroundings are not illuminated. This is in contrast to light objects, such as “_PointLight” which emit light and thereby illuminate nearby objects. “_MeshLight” objects don’t use additional processing power, but “_PointLight” objects do and this will reduce system performance.

The night time glow effect is achieved by assigning two textures to an object – a base texture and an emission texture.

The definition of the luminous colours is done by the emission texture. When the light is off, the base texture is shown, but when the light is on, the non-black areas of the emission texture are shown. Any areas of ​​the emission texture with the colour of the base texture do not light up.

Emission texture: Only the green lettering and the red border light up with the light on. In the black area, the colour of the basic texture is shown, blue in the example below.

This results in two use cases:

The base texture and the emission texture have the luminous areas the same colour.

The base texture and the emission texture have in the luminous areas different colours.

With this arrangement in the MBS*
(left light off, right light on)

With this arrangement in the MBS*
(left light off, right light on)

The starting point is a cube…

In this case, the MBS* has one possible
colour change. The object’s name must start with “_MeshLight” but the suffix is set by the user.

Assigning the base texture…

and the assignment of the emission texture…

With this result in MBS* (left light off, right light on)

Blender allows the emission strength to be specified as a parameter to set the degree of luminousity. Valid values ​​range from 0 to 1. Although values ​greater than 1 can be set in Blender, the .gltf / .glb exporters limit the maximum to 1 so that no further gain in brightness is realised with higher values.

The result in the MBS* with the light on:

*MBS: Model Building Specification