In today’s tutorial, we’ll take a detailed look at the various light sources available in Unreal Engine 5, exploring where and when to use them:
- Directional Light
- Point Light
- Spot Light
- Rect Light
- Sky Light
- HDRI Backdrop
Most of these light sources share the same features, so I won’t repeat a feature if I’ve already covered it. Just a heads up!
1-) Directional Light
What does it do?
- Simulates sunlight or moonlight.
- Casts light in a single direction across the entire scene.
- Affects large areas and is used for outdoor environments.
Where to use:
- When you need to light large, open spaces. (Lighting an outdoor landscape during daytime.)
- Ideal for creating daylight or moonlight effects. (Simulating moonlight in an outdoor night scene.)
Parameters:
- Intensity: Brightness strength.
- Light Color: Defines the color of the light emitted.
- Source Angle: Affects the softness of shadows. Higher the value, softer the shadows, and vice-versa.
- Source Soft Angle: Softens the edges of shadows. You might need to type in very high numbers to get the desired result. By default it looks like it’s limited to 5 max, but you can go way beyond that.
- Use Temperature: Should Kelvin color scale temperature be used or not?
- Temperature: What should be the Kelvin value?
- Affects World: True/False?
- Cast Shadows: True/False?
- Indirect Lighting Intensity: Adjusts the strength of indirect lighting (light bouncing off surfaces — Light that hits a surface and then reflects off that surface to illuminate other parts of the scene: Sunlight hitting a white wall and the reflected light illuminating the room with a soft glow.).
- Volumetric Scattering Intensity: Determines the intensity of the light scattering through volumetric materials (e.g., fog, smoke). Increase to make the light more visible as it passes through particles or fog, enhancing the sense of atmosphere.
Useful for creating god rays or enhancing environmental effects.
2-) Point Light
What does it do?
- Emits light in all directions from a single point. (Similar to a light bulb.)
Where to use:
- For localized light sources. (A lamp in a room.)
- Good for indoor environments where light is needed in specific areas. (A streetlight on a city street.)
Parameters:
- Intensity Units: Candelas: This method uses the light source’s brighness in one specific direction, think of how intense a flashlight beam is and how it affects the world. — Unitless: Physically inaccurate, it cares more about how the light looks. — Lumen: Measures the total amount of light coming from the source, like the overall brightness of a light bulb.
- Attenuation Radius: Determines how far the light reaches from its source. In other words increasing it makes the light affect a larger area.
- Source Radius: The physical size of the light source. Affects the softness of the shadows cast by the light. Larger source radius creates softer, more diffuse shadows. Smaller source radius creates sharper shadows.
- Soft Source Radius: Similar to ‘Source Radius’ but specifically controls the softness of the edges of the light source. Influences the transition between fully lit and shadowed areas. Larger values create smoother transitions and softer edges.
- Source Length: Primarily affects the shape and directionality of the light. Useful for simulating long, narrow light sources like fluorescent tubes or strip lights. Can affect the appearance of shadows, making them longer or more diffuse depending on the setup. Can be used to create light patterns such as elongated, etc.
3-) Spot Light
What does it do?
- Emits a cone of light from a single point.
- Similar to a flashlight or stage spotlight.
Where to use:
- When you need to highlight specific objects or areas.
- Useful for dramatic lighting effects. A flashlight beam in a dark environment.
Parameters:
- Inner Cone Angle: Sets the angle of the inner cone of the spotlight. A smaller angle creates a more focused beam, while a larger angle widens the cone.
- Outer Cone Angle: Sets the angle of the outer cone of the spotlight. Defines the total angle of the light cone emitted by the spotlight. The area between the inner and outer cone angles represents the falloff of the spotlight’s intensity.
- Indirect Lighting Saturation: Modifies the strength of the light’s influence on indirect illumination in the scene. Higher saturation intensifies the color influence of the spotlight on surrounding surfaces.
- Shadow Exponent: Modifies the softness of the spotlight’s shadows. Increasing the exponent creates softer shadows.
- Use Area Shadows for Stationary Light: Improves the quality of shadows by simulating the light source’s physical size. Recommended for realistic shadow rendering, especially with larger spotlight sources.
- Max Draw Distance: Sets the maximum distance at which the spotlight is visible and affects the scene. Optimizes performance by limiting the rendering impact of distant lights.
- Max Distance Fade Range: Defines the distance range over which the spotlight’s intensity fades. Can be used to create smooth fades of the light’s influence beyond a specified distance.
- IES Texture: Provides realistic light distribution based on real-world light fixtures. Uses IES (Illuminating Engineering Society) profile texture. Epic’s official documentation provides more than enough information on how to implement it, where to get these textures, etc.
- Samples Per Pixel: Determines the quality and smoothness of the spotlight’s appearance, especially in shadowed areas.
Example: Higher values result in smoother shadows and more accurate light representation, but can impact performance.
4-) Rect Light
What does it do?
- Emits light from a rectangular area.
- Provides soft, even lighting, similar to a fluorescent panel or softbox in photography.
Where to use:
- When you need broad, even lighting over a large area.
- Great for studio lighting or soft light sources.
Parameters:
- Barn Door Angle: Adjust the angle to restrict or focus the light beam in a specific direction.
- Barn Door Length: The length of the barn doors, which further helps in shaping and controlling the light beam. Modify the length to fine-tune the shape and directionality of the light.
- Source Texture: The texture applied to the light source, which can affect the appearance and behavior of the emitted light.
5-) Sky Light
What does it do?
- Captures ambient light from the environment and casts it into the scene.
- Simulates indirect lighting from the sky.
Where to use:
- To create ambient outdoor lighting. Enhances realism by providing environmental reflections. Simulating the ambient light of a cloudy day.
Parameters:
- Cubemap: A texture used to represent the surrounding environment and simulate distant lighting and reflections.
- Source Cubemap Angle: Controls the angle of the cubemap used for the sky light.
- Cubemap Resolution: Determines the quality and detail of the cubemap texture. Higher resolution means sharper and clearer reflections.
- Sky Distance Threshold: Defines the distance at which the sky light starts to fade out or blend with other lighting sources.
- Intensity Scale: Adjusts the overall brightness or intensity of the sky light.
- Occlusion Max Distance: Sets the maximum distance at which occlusion affects the sky light. When light rays from the sky hit objects like buildings, trees, or terrain, they can cast shadows or block the light, creating darker areas on surfaces that are not directly exposed to the sky. Occlusion Max Distance defines the furthest distance from the sky light source where occlusion effects are considered. Beyond this distance, objects will have less or no impact on blocking the sky light.
- Occlusion Contrast: Controls the contrast of occlusion, influencing how dark or light the occluded (areas where skylight is blocked) areas appear.
- Occlusion Exponent: Adjusts the falloff rate of occlusion, affecting how quickly occlusion changes from full darkness to full brightness.
- Min Occlusion: Sets the minimum level of occlusion, defining the darkest possible shadowed areas. We just mentioned that we can control at what distance objects can block the skylight. When they block the light, they might generate shadows. This option allows us to specify the minimum amount of occlusion applied to shadowed areas. Setting a low minimum occlusion level helps us create deep, dark shadows and increasing the value on the other hand, lightens the shadows, making the scene appear brighter and more evenly lit.
- Occlusion Tint: Adds a color tint to occluded areas, influencing the tone of shadows.
- Occlusion Combine Mode: (OCM Minimum — OCM Multiply): Selects how multiple occlusion calculations are combined to produce the final result (e.g., using the darkest shadow value or multiplying occlusion values). OCM Minimum is useful for maintaining strong contrast and preserving detail in shadowed areas. It can be very effective in scenes where you want distinct, well-defined shadows, such as for dramatic lighting effects. OCM Multiply can potentially create deeper, darker and more uniform shadows.
- Cloud Ambient Occlusion: Enables ambient occlusion (AO simulates the indirect lighting that occurs when objects block or scatter light in a scene and softens harsh lighting transitions while adding natural-looking shadowing.) calculations specifically for cloud shadows.
- Cloud Ambient Occlusion Strength: Adjusts the strength or intensity of cloud ambient occlusion.
- Cloud Ambient Occlusion Extent: Defines the extent or range over which cloud ambient occlusion is applied.
- Cloud Ambient Occlusion Map Resolution Scale: Controls the resolution of the ambient occlusion map used for clouds, affecting detail and quality.
- Cloud Ambient Occlusion Aperture Scale: Adjusts the aperture size used for cloud ambient occlusion calculations.
- Show Illuminance Meter: Displays a visual meter or indicator showing the amount of light intensity in the scene.
- Recapture Scene?: Triggers a recalculation or update of the sky light, capturing changes in the scene or environment.
6-) HDRI Backdrop (Needs to be enabled through the ‘Plugins’ window first.)
What does it do?
- Enables developers to use HDRs in Unreal Engine. (Usully combined with Directional Light since HDRI Backdrop generates no shadows.)
Where to use:
- Can be used as environment lighting sources to contribute to the overall lighting and ambient occlusion in a scene, which can indirectly affect the appearance of shadows.
Final Words
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