How to Fix Overlapping Lights Unreal Engine

Overlapping lights in Unreal Engine can cause visual glitches, performance drops, and unrealistic lighting. This guide shows you how to identify, troubleshoot, and fix overlapping lights using built-in tools and best practices for cleaner, more efficient scenes.

Key Takeaways

Understand the causes of overlapping lights: Multiple lights affecting the same area can create artifacts, double shadows, or performance issues.
Use the Light Complexity view mode: This visual tool helps you spot overlapping lights by showing color-coded complexity levels in your scene.
Adjust light mobility settings: Switch between Static, Stationary, and Movable lights based on your scene needs to reduce overlap and improve performance.
Optimize light influence with attenuation and radius: Fine-tune the radius and falloff of your lights to minimize unnecessary overlap.
Leverage Lightmass settings for baked lighting: Properly configure Lightmass to avoid overlapping shadows and improve lighting quality in static scenes.
Use Light Functions and IES profiles wisely: These can enhance realism but may contribute to overlap if not managed carefully.
Test and iterate in different lighting conditions: Always preview your scene in various times of day and environments to catch hidden overlaps.

How to Fix Overlapping Lights in Unreal Engine

Lighting is one of the most important aspects of creating immersive and visually appealing environments in Unreal Engine. Whether you’re building a realistic indoor scene or a sprawling open world, proper lighting enhances mood, depth, and realism. However, one common issue that many developers and artists face is overlapping lights—when multiple light sources affect the same area in a scene. This can lead to visual artifacts, performance problems, and inconsistent lighting behavior.

In this comprehensive guide, you’ll learn exactly how to fix overlapping lights in Unreal Engine. We’ll walk you through identifying the problem, understanding why it happens, and applying practical solutions using Unreal Engine’s built-in tools and best practices. By the end, you’ll have a clean, optimized lighting setup that looks great and runs smoothly.

What Are Overlapping Lights?

Overlapping lights occur when two or more light sources illuminate the same area in your scene. This isn’t always a bad thing—sometimes, multiple lights are used intentionally to create soft shadows or realistic ambient lighting. However, when lights overlap unintentionally or excessively, they can cause several issues:

Double or conflicting shadows: Objects may cast multiple shadows or have inconsistent shadow directions.
Light bleeding or artifacts: Bright spots, flickering, or unnatural color blending can appear.
Performance drops: Each light adds computational cost, especially dynamic ones. Overlapping increases GPU and CPU load.
Inconsistent lighting: The final look may vary between editor and packaged builds due to lighting calculations.

Understanding the root causes helps you prevent and fix these problems effectively.

Why Do Lights Overlap in Unreal Engine?

Before diving into fixes, it’s important to know why overlapping happens in the first place. Here are the most common reasons:

1. Multiple Lights with Large Radii

When lights have wide influence radii, they naturally cover large areas. If two or more such lights are placed close together, their influence zones will overlap. This is especially common with point lights and spotlights used for general illumination.

Visual guide about How to Fix Overlapping Lights Unreal Engine

Image source: i.imgur.com

2. Incorrect Light Mobility Settings

Unreal Engine offers three light mobility types: Static, Stationary, and Movable. Using the wrong type can cause unintended overlap. For example, placing multiple Stationary lights in a small area can lead to overlapping baked and dynamic lighting.

3. Poor Light Placement

Placing lights too close together without considering their falloff or direction can create hotspots and overlapping illumination. This is common in interior scenes with ceiling lights or outdoor scenes with multiple street lamps.

4. Overuse of Dynamic Lighting

Dynamic lights (Movable) are calculated in real-time and can stack their effects. Too many dynamic lights in one area can overwhelm the renderer and cause visual noise.

5. Baked Lighting Artifacts

When using Lightmass to bake static lighting, overlapping lights can create artifacts in the lightmap, such as dark spots or incorrect shadow blending.

Now that you know the causes, let’s move on to diagnosing and fixing the problem.

Step 1: Identify Overlapping Lights Using View Modes

The first step in fixing overlapping lights is to detect them. Unreal Engine provides several view modes that help visualize lighting complexity and identify overlaps.

Use the Light Complexity View Mode

This is one of the most effective tools for spotting overlapping lights. It color-codes areas based on how many lights are affecting them.

In the main viewport, click on the View Mode dropdown (usually in the top-left corner).
Navigate to Optimization Viewmodes > Light Complexity.
The scene will now display colors:
- Black: No lights affecting the area.
- Green: 1–2 lights (ideal).
- Yellow: 3–4 lights (caution).
- Red: 5+ lights (overlap likely).

Areas showing red or bright yellow indicate potential overlapping lights. Focus on these zones first.

Check Lightmap Density

Overlapping lights can also cause issues in lightmap resolution. Use the Lightmap Density view mode to ensure your static lights are baking properly.

Go to View Mode > Optimization Viewmodes > Lightmap Density.
Ideal areas should show green (good resolution). Red areas mean too much detail; blue means too little.
If overlapping lights are causing high density in small areas, consider reducing light count or adjusting Lightmass settings.

Use Shader Complexity View Mode

This mode shows how many shader instructions are being used per pixel. Overlapping lights increase shader workload.

Select View Mode > Optimization Viewmodes > Shader Complexity.
Red areas indicate high complexity—often due to multiple overlapping lights or materials.

These view modes give you a clear picture of where overlaps are happening and how severe they are.

Step 2: Adjust Light Radius and Attenuation

One of the simplest ways to reduce overlapping is to fine-tune the radius and falloff of your lights.

Reduce Light Radius

If a light has a large radius, it affects more of the scene than necessary. Shrinking the radius limits its influence and reduces overlap.

Select the light in the viewport or World Outliner.
In the Details panel, find the Light section.
Adjust the Attenuation Radius to a smaller value.
Use the Radius visualization (a sphere around the light) to see the current influence area.

Tip: Start with a radius just large enough to cover the intended area. Avoid making it too big “just in case.”

Tweak Light Falloff

Falloff controls how quickly the light diminishes over distance. A sharper falloff reduces overlap by limiting how far the light reaches.

In the light’s Details panel, look for Light Falloff Exponent.
Increase the value for a sharper falloff (e.g., from 2.0 to 4.0).
Higher values make the light drop off faster, reducing overlap with nearby lights.

Example: A point light with a radius of 500 units and a falloff exponent of 4.0 will have a much tighter influence than one with an exponent of 2.0.

Use Light Channels

Light channels allow you to control which lights affect which objects. This is useful for isolating lights and preventing unwanted overlap.

Select the light and go to the Light Channels section.
Assign the light to a specific channel (e.g., Channel 1).
Select the objects you want the light to affect and enable the same channel in their Lighting settings.

This way, you can have multiple lights in the same area without them all affecting every object.

Step 3: Optimize Light Mobility Settings

Choosing the right mobility type is crucial for both performance and lighting quality.

Understand the Three Mobility Types

Static: Baked into lightmaps. Cannot move or change. Best for non-moving lights like ceiling fixtures. No runtime cost.
Stationary: Can change intensity, color, or toggle on/off, but position is fixed. Partially baked. Moderate cost.
Movable: Fully dynamic. Can move, change, and cast real-time shadows. Highest cost.

Choose the Right Type for Each Light

Overlapping often occurs when too many Stationary or Movable lights are used in one area. Here’s how to fix it:

Use Static lights for permanent fixtures: If a light won’t move or change, make it Static. This reduces runtime overlap and improves performance.
Limit Stationary lights: These are great for lights that need to flicker or dim, but avoid clustering them. Use them sparingly in small areas.
Reserve Movable lights for dynamic objects: Only use Movable lights for things like flashlights, car headlights, or moving characters. They should be the exception, not the rule.

Example: In a room with four ceiling lights, make them all Static. If one needs to turn on/off, make only that one Stationary—others stay Static.

Convert Lights When Possible

If you have multiple Stationary lights overlapping, consider converting some to Static if their behavior doesn’t need to change.

Select the light.
In the Details panel, change Mobility from Stationary to Static.
Rebuild lighting (Build > Build Lighting Only).

This reduces dynamic lighting calculations and can eliminate overlap artifacts.

Step 4: Use Lightmass Settings to Fix Baked Lighting Overlaps

For static and stationary lights, Lightmass handles the baking process. Incorrect settings can cause overlapping shadows or light bleeding.

Adjust Lightmass Settings

Go to World Settings > Lightmass and tweak these key settings:

Static Lighting Level Scale: Lower values (e.g., 0.5) increase lightmap resolution, reducing artifacts. Default is 1.0.
Num Indirect Lighting Bounces: Controls how many times light bounces. Too many can cause overlapping glow. Start with 4–6.
Indirect Lighting Quality: Higher values improve accuracy but increase bake time. Use 2–4 for most scenes.
Environment Intensity: If using an HDRI sky, this can add ambient light. Too high can wash out or overlap with other lights.

Rebuild Lighting After Changes

After adjusting Lightmass settings, always rebuild lighting:

Click Build > Build Lighting Only.
Wait for the process to complete.
Check the scene for improvements in overlap and shadow quality.

Tip: Use Build > Build All if you’ve also changed geometry or materials.

Step 5: Manage Dynamic Lighting and Real-Time Shadows

Dynamic lights (Movable) are the most likely to cause overlapping because they’re calculated in real-time.

Limit the Number of Dynamic Lights

Unreal Engine has limits on how many dynamic lights can affect a single object. Too many can cause clipping or overlap.

Use the Max Dynamic Shadow Lights setting in Project Settings > Rendering > Shadows.
Default is usually 4–8. Lower it if you’re seeing overlap in dynamic scenes.

Use Capsule Shadows for Characters

Instead of full dynamic shadows for characters, use capsule shadows to reduce overlap and improve performance.

Select the character mesh.
In the Details panel, enable Cast Capsule Direct Shadow.
This creates a simplified shadow that doesn’t conflict with other lights.

Disable Shadows on Non-Essential Lights

If a light doesn’t need to cast shadows (e.g., a soft fill light), turn them off.

Select the light.
In the Details panel, uncheck Cast Shadows.
This reduces overlap and improves performance.

Step 6: Use Light Functions and IES Profiles Carefully

Light Functions and IES profiles add realism but can contribute to overlap if overused.

Understand Light Functions

Light Functions allow you to modify a light’s intensity or color using textures or materials. They’re great for effects like flickering or patterned light.

Avoid Overlapping Light Functions

If multiple lights use complex Light Functions, their effects can stack and create visual noise.

Use Light Functions only when necessary.
Keep them simple—avoid high-frequency textures that cause flickering.
Test in different lighting conditions to ensure they don’t clash.

Use IES Profiles Sparingly

IES profiles simulate real-world light distribution. They’re great for accuracy but can cause hotspots if multiple lights use similar profiles.

Assign IES profiles only to key lights (e.g., street lamps).
Avoid using them on every light in a scene.
Check the Light Complexity view mode after applying IES profiles.

Step 7: Test and Iterate in Different Conditions

Lighting can look different at various times of day or in different environments. Always test your scene thoroughly.

Use Time of Day Systems

If your scene uses a day/night cycle, test lighting at multiple times.

Use a Sky Atmosphere or Exponential Height Fog with time controls.
Preview at dawn, noon, dusk, and night.
Look for overlapping lights that only appear in certain conditions.

Test in Packaged Builds

Lighting can behave differently in the editor vs. a packaged game.

Package your project (File > Package Project).
Run the build and check for overlaps or artifacts.
Fix any issues and repackage if needed.

Troubleshooting Common Overlap Issues

Problem: Double Shadows on Objects

Solution: Check if multiple lights are casting shadows on the same object. Disable shadows on non-essential lights or adjust their positions.

Problem: Flickering or Flickering Lights

Solution: This is often caused by overlapping dynamic lights or incorrect Lightmass settings. Reduce the number of dynamic lights or increase Indirect Lighting Quality.

Problem: Bright or Washed-Out Areas

Solution: Lights may be too intense or overlapping too much. Lower the intensity or radius of overlapping lights.

Problem: Performance Drops in Complex Scenes

Solution: Use the Shader Complexity and Light Complexity view modes to identify problem areas. Convert lights to Static or reduce their count.

Best Practices to Prevent Overlapping Lights

Plan your lighting layout: Sketch or block out light positions before placing them.
Use reference images: Study real-world lighting to understand how lights interact.
Start simple: Begin with one key light, then add fill and rim lights as needed.
Name your lights: Use clear names like “CeilingLight_Kitchen” to keep track.
Regularly rebuild lighting: Especially after adding or moving lights.
Use lighting layers: Organize lights into groups for easier management.

Conclusion

Fixing overlapping lights in Unreal Engine doesn’t have to be frustrating. By using the right tools—like Light Complexity and Shader Complexity view modes—and applying smart lighting practices, you can create clean, efficient, and visually stunning scenes. Remember to adjust light radii, choose the correct mobility type, optimize Lightmass settings, and test thoroughly.

Overlapping lights are a common challenge, but with the steps in this guide, you now have a clear roadmap to solve them. Whether you’re working on a small interior or a massive open world, proper lighting management will elevate your project’s quality and performance.

Take the time to iterate, test, and refine. Your players and audience will notice the difference.