**4. Lighting setting**

Lights in 3D virtual environments are necessary for objects to be visible. The same logic applies in real world. Without light, it is not possible to see your surroundings. There are several types of lights, but most common are *directional light*, *point light*, *spotlight*, and *ambient light*. The difference between these lights is ways of lighting up a specific area, where a light source and lighting direction is located. Lighting itself works basically the same. Light has defined its source, direction, intensity, and area, then this parameter defines the vectors which are colliding and bouncing from the objects in dependence on how close the light source is, how strong light intensity is, and area of light up space. Wheelchair simulator uses ambient light in all scenes. **Figure 3** represents scenes with ambient lightning.

One of the scenes is designed to be at night. Scene is called crosswalk-night. As is mentioned above, ambient light is everywhere and it illuminates every object evenly from every side. **Figure 4** shows the scene.

**Figure 3.** *Four out of five scenes with ambient lighting.*

**Figure 4.** *Representation of crosswalk-night scene.*

It is possible to observe that besides ambient light, fog is implemented as well. Fog allows to shade the objects at a certain distance in a predetermined color. It is implemented on camera of the user and not as a light object. Therefore, fog is not perceived as a lighting setting but as a shading setting. In this case, distance of shading is few meters from the user, and color of shading is black. This way it is possible to simulate first-person view at night, samely as in real life. From **Figure 4**, it is also possible to see the red traffic light, which signals that patient cannot cross the crosswalk as cars are moving. The red color on a box may seem a lot lighter than surroundings. It is because of emissive intensity of material on a traffic light was set on a higher value to make it
