- Description
- Parameters Found In All Light Types
- Light Type: Directional Light
- Light Type: Point Light
- Light Type: Spotlight
- Light Type: Rect Light
- Light Type: HDRi Backdrop & HDRi Skylight
- Final Words
- Questions Came From You Through Patreon
Content Index – Click to jump to the desired section.
Unreal Engine 5: Explaining Light Types and Their Parameters
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. Most of these light sources share the same features, so I thought it would be better to go through these common options first, then focus on the light-type-specific options. In this tutorial, I won’t be covering volumetric clouds, since it’s not an option that I use in my projects very often. However, if there is a demand for it, please make a request by writing to me here, and I can create a dedicated tutorial for it later. I covered the most important parts of SkyAtmosphere here; therefore, I won’t be diving into it again, so if you’re interested, you can check the tutorial here.Without further ado, let’s get started!
Parameters Found In All Light Types
- Intensity: Brightness strength.
- Light Color: Defines the color of the light emitted.
Source Radius/Source Angle: The "physical" size of the light source. The Source Angle option is only available in Directional Lights, while the Source Radius option is available for other types of lights. In essence, they are doing the same thing: directly affecting the softness of shadows. The reason this option is named differently for Directional Lights is because a Directional Light is considered to be the sun or moon, therefore it needs to be “infinite” (think of how the real sun isn’t a single point of light), and the radius needs to be measured in degrees. The real-world value for this option would be ~0.53°. Larger source angle means that the sun appears bigger in the sky. I dived into the details of this matter in this post if you’d like to read more about it, but back to the Source Angle: the higher the value we have here, the softer our shadows will become, and vice versa. For example, a value of ~0.1° would give us very sharp shadows, like crisp sunlight on a clear day. Larger angles (0.5°–1° or more) mean that shadows become softer, edges blur, and the result can be considered more realistic for slightly hazy or cinematic skies. Lower values such as 0.1° result in very sharp shadows and a crisp sun disk. For clear skies, 0.3° is considered a go-to value, since it provides slightly softened shadows. The most natural look usually falls between 0.5°–0.6°: soft shadows again, but this time with a subtle atmospheric halo. Values of 1° or higher result in very soft shadows and a sun that looks quite large; these are generally not suggested unless you’re going for a more stylized or hazy atmosphere.
Source Angle (Directional Light Only): 5
Source Angle (Directional Light Only): 50
Source Radius: 0 vs 5000 vs 100
Source Radius: 0 vs 1000
- Soft Source Radius (Other Light Types) - Source Soft Angle (Directional Light Only): 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. A detailed guide to this option can be found here on this page.
Soft Source Radius: 0 vs 1024
Soft Source Radius: 0 vs 1024
- Use Temperature: Should the Kelvin color scale temperature be used or not? Please refer to this tutorial for a detailed explanation and its usage in Blender 3D and Unreal Engine 5.
- Temperature: What should be the Kelvin value?
- Affects World: True/False?
- Cast Shadows: True/False? Can come in handy to optimize your scenes. Not every light source needs to cast a shadow. And as we talked about in the optimization guide here, shadows are one of the most expensive things in game engines.
- Indirect Lighting Intensity: Adjusts the strength of indirect lighting. What is indirect lighting then? When an emitted light hits a surface in real life, it bounces off and hits other surfaces close to the hit point, illuminating the surroundings of the hit area as well. I think a good example would be to think of sunlight hitting a white wall and the reflected light illuminating the room with a soft glow. One important thing to note: Indirect Lighting Intensity affects baked (static or stationary) lighting, not fully dynamic lighting (movable lights, for example). During baking, some details or the intensity of the light sources might be lost due to the lightmap UVs of the 3D assets or the lightmap resolution being too small, like 64×64 px. This option basically lets you increase or decrease the intensity of the baked lights.
- 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.
- Intensity Units: Candelas: This method uses the light source’s brightness 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. One very important thing to pay attention to is that Unreal Engine doesn’t like colliding light sources, since it needs some extra light-bouncing calculations. In fact, there is a limitation on how many stationary light sources, for example, can overlap with each other. Try to keep the attenuation radius and source radius of a light source from colliding with another one as much as possible.
- 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.
- Source Texture: The texture applied to the light source, which can affect the appearance and behavior of the emitted light.
Light Type: Directional Light
- Simulates sunlight or moonlight.
- Casts light in a single direction across the entire scene.
- Affects large areas and is used for outdoor environments.
What does it do?
- 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.)
Where to use:
2. Point Light
- Emits light in all directions from a single point. (Similar to a light bulb.)
What does it do?
- 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.)
Where to use:
Your advertisement can be placed here for $200 permanently. Suggested resolutions: 1800x663 or 1400x1400. Contact us.
3. Spot Light
- Emits a cone of light from a single point.
- Similar to a flashlight or stage spotlight.
What does it do?
- When you need to highlight specific objects or areas.
- Useful for dramatic lighting effects. A flashlight beam in a dark environment.
Where to use:
- 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.
Parameters:
4. Rect Light
- Emits light from a rectangular area.
- Provides soft, even lighting, similar to a fluorescent panel or softbox in photography.
What does it do?
- When you need broad, even lighting over a large area.
- Great for studio lighting or soft light sources.
Where to use:
- 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.
Parameters:
HDRi Backdrop & HDRi Skylight (Needs to be enabled through the ‘Plugins’ window first.)
- Places a real life sky texture/dome into the scene. In other words it enables developers to use HDRs in Unreal Engine. (Usully combined with Directional Light since HDRI Backdrop generates no shadows.)
- Captures ambient light from the environment and casts it into the scene.
- Simulates indirect lighting from the sky.
What does it do?
- To create realistic skies and ambient outdoor lighting. HDRi ambient cubemap enhances realism by providing environmental reflections.
Where to use:
- 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. Rotates the HDRI cubemap used by the Sky Light without rotating the actual HDRIBackdrop dome. Useful when: You want to rotate the light direction but keep the backdrop image fixed Or vice-versa It rotates only the lighting information, not the visible background sphere.
Parameters:
Source Cubemap Angle: 0
Source Cubemap Angle: 115
- Cubemap Resolution: Determines the quality and detail of the cubemap texture. Higher resolution means sharper and clearer reflections. Defines the resolution of the HDRi cubemap used for lighting. Higher = sharper lighting detail + more accurate reflections, but heavier on performance. Common values: 256 or 512: fine for games 1024+: for cinematic quality
Cubemap Resolution: 8
Cubemap Resolution: 256
Cubemap Resolution: 512
Cubemap Resolution: 2048
- Sky Distance Threshold: Defines the distance at which the sky light starts to fade out or blend with other lighting sources.
- Sky Distance Threshold: Intensity Scale: Adjusts the overall brightness or intensity of the sky light. There are two of these, one located in hdri parent component itself, which adjusts the brightness of the hdri texture itself, and the second one found in the geometry component.
Adjusting the intensity here in this component will increase the brightness of the sky texture, but not the lighting intensity (ambient cubemap/skylight of the HDRi) of the world.
To enable and assign an ambient cubemap to the HDRI Backdrop, we gotta switch to the Geometry tab, set the Source Type from “SLS Captured Scene” to “Cubemap”, and select the same HDRI texture you’re using for your sky.
- 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.
Final Words
In the future I'd like to extend this tutorial, make it more detailed and provide more screenshots to be better understood. If you'd like to see this website growing and you are a fan of written tutorials instead of video ones, please consider supporting this website. If there are any confusing parts or if there’s something you’d like to add, please feel free to share your thoughts
Questions Came From You Through Patreon
- Can you have multiple directional lights in your level?
Techically yes, Unreal would allow you to have as many directional lights as you want, but for a real game level, one main light (sun) is the standard. Also placing multiple directional lights will not give you extra shadows, after the first one the other ones are treated as "fillig light".
Do you need a skylight if your level already has an HDRI and a directional light?
No, you don’t need a Skylight if you already have an HDRI Backdrop and a Directional Light.