Lights

Evergine uses an advanced lighting model to simulate how light affects geometries. It also supports multiple lights in the scene, allowing a wide range of environments and possibilities.

Every type of light is modeled in Evergine using a Light component.

Create a Light in Evergine Studio

In the Entities Hierarchy panel of your Scene Editor, click "Add Entity," select Light, and then choose the kind of light you want to create:

Point Light
Directional Light
Sphere Area Light
Spot Light
Disc Area Light
Rectangle Area Light
Tube Area Light

We discuss the light types later in this article.

Create Light

Additionally, we can create photometric lights from the same panel with these options:

Photometric Point Light
Photometric Directional Light
Photometric Sphere Area Light
Photometric Spot Light
Photometric Disc Area Light
Photometric Rectangle Area Light
Photometric Tube Area Light

Create Light

Create Light from Code

The following sample code can be used to instantiate a new basic point light entity in a scene.

protected override void CreateScene()
{
    // Create a new light entity.
    Entity pointLightEntity = new Entity()
        .AddComponent(new Transform3D())
        .AddComponent(new PointLight()
        {
            Color = Color.Red,
            Intensity = 3,
            LightRange = 10
        });

    // Add the light entity to the entity manager.
    this.Managers.EntityManager.Add(pointLightEntity);
}

Basic Light Properties

These are the basic properties that almost all lights have.

Property	Description
Is Enabled	If the light is on/off.
Shadow Enabled	Enable/disable shadow mapping for this light.

Photometric / Non-Photometric Lights

Photometric lights use photometric (lighting units) allowing you to define lights as they would be in the real world. They are configured using physical parameters. Evergine supports both photometric and non-photometric lights, and it offers the same light types duplicated based on this choice.

Common Photometric Properties

Every photometric light (no matter what type it is) defines these parameters. Additionally, each specific type of light defines its own intensity unit properties.

Property	Description
Color By Temperature	Indicates if the light color will be overridden using the light temperature.
Temperature	The light temperature in Kelvin (K). When ColorByTemperature is true, the light color is overridden by the light temperature.

Note

Light intensity unit depends on the light type (for example, PointLights are measured in Lumens, whereas DirectionalLights are measured in Lux).

Non-Photometric Light Properties

On the contrary, if you create regular lights, you can use the basic light properties:

Property	Description
Color	The RGB color tint of the light.
Intensity	The light intensity value in a non-standard unit. Greater values will produce brighter illumination.

Types of Lights

There are different types of lights, each useful for a different scenario. In general terms, lights are divided into two general categories:

Directional Lights: These lights have unlimited boundaries, and every object is affected by this light type.
Volume Lights: The light influence is delimited by a range.
Area Lights: A subtype of volume lights that emulate lights coming from an area instead of a point in space.

Directional Lights / Photometric Directional Light

Directional Light

Directional lights are lights that come uniformly from one direction and at an infinite distance. They're used to simulate distant light sources like the sun. They use the forward vector of their entity's Transform3D for calculating the light direction.

In the case of using a Photometric Directional Light, the intensity is measured using the following property:

Photometric Property	Description
Illuminance (Lux)	The light illuminance measured in Lux. Indicates the total luminous flux incident on a surface, per unit area.

Volume Lights

Volume lights are a common type of light in which the light source comes from a specific point in space, and its intensity decays with distance.

Property	Description
Light Range	The light range in meters.

In the case of using Volume Photometric Lights, the intensity is measured using the following property:

Photometric Property	Description
Luminous Power (Lumen)	The light luminous flux in Lumen.

Point Light / Photometric Point Light

Point Light

A point light is located at a point in space and emits light equally in all directions within its sphere range. Its intensity decays with distance from the light, reaching zero at its maximum range. It's useful for local lights like lamps.

Spot Light / Photometric Spot Light

Spot Light

A spot light is also placed in a specific location and has a range over which the light decays. However, spot lights are constrained by an angle, defining a cone-shaped light.