How to Fix Lighting in Unreal Engine 4

Struggling with dark, flickering, or unrealistic lighting in Unreal Engine 4? This guide walks you through common lighting issues and practical fixes to improve visual quality and performance. Master lighting setup, troubleshooting, and optimization for stunning results.

Key Takeaways

• Understand lighting types: Learn the differences between static, stationary, and movable lights to choose the right one for your scene.
• Use Lightmass settings wisely: Adjust Lightmass settings like Indirect Lighting Quality and Bounce to improve lighting accuracy and reduce noise.
• Check lightmap resolution: Low lightmap resolution causes blurry shadows; increase it in Static Mesh settings for sharper results.
• Rebuild lighting properly: Always rebuild lighting after changes to see accurate results and avoid dark or missing light.
• Optimize with Light Propagation Volume: Use LPV for dynamic global illumination in large, open worlds with moving lights.
• Debug with visualization tools: Use Unreal’s lighting visualization modes to spot problems like light leaks or incorrect shadows.
• Balance quality and performance: Tweak settings to maintain visual fidelity without hurting frame rates, especially on lower-end hardware.

How to Fix Lighting in Unreal Engine 4

Lighting is one of the most important aspects of creating immersive and believable environments in Unreal Engine 4 (UE4). Whether you’re building a realistic outdoor landscape, a moody indoor scene, or a stylized game world, good lighting can make or break the visual quality. Unfortunately, many developers—especially beginners—run into common lighting problems like dark areas, flickering shadows, light leaks, or performance drops.

In this comprehensive guide, you’ll learn how to fix lighting in Unreal Engine 4 step by step. We’ll cover everything from understanding light types and adjusting Lightmass settings to troubleshooting common issues and optimizing for performance. By the end, you’ll have the tools and knowledge to create stunning, well-lit scenes that look great and run smoothly.

Understanding Lighting Types in Unreal Engine 4

Before diving into fixes, it’s essential to understand the three main lighting modes in UE4: Static, Stationary, and Movable. Each has different performance costs and use cases.

Static Lighting

Static lights are baked into lightmaps and don’t change during gameplay. They’re the most performance-friendly but only work for non-moving objects. Use static lighting for environments where lighting doesn’t need to change, like a pre-rendered level or a scene with fixed light sources.

Stationary Lighting

Stationary lights are a hybrid option. They can have some dynamic properties—like changing intensity or color—but their position and shadows are precomputed. This makes them ideal for lights that need subtle animation, such as a flickering lamp or a dimming streetlight, without the high cost of fully dynamic lighting.

Movable Lighting

Movable lights are fully dynamic and update in real time. They’re perfect for moving light sources like car headlights or a character holding a flashlight. However, they’re the most performance-intensive and should be used sparingly.

Tip: Always choose the light type that matches your needs. Using movable lights for static objects is a common mistake that hurts performance.

Setting Up Your Scene for Proper Lighting

A well-lit scene starts with a solid foundation. Here’s how to prepare your level for optimal lighting.

Use Real-World Scale

Unreal Engine works best when objects are modeled to real-world scale. A room that’s 10 unreal units wide will look and behave differently than one that’s 10 meters (about 1000 units). Incorrect scaling can cause lighting to look off—shadows may be too sharp or too soft, and light intensity might seem unrealistic.

To check scale, use the Grid Snap tool and compare your meshes to the default mannequin (which is roughly 180 cm tall). Most architectural elements should align with real-world dimensions.

Ensure Proper Geometry

Lighting relies on accurate geometry. Gaps between walls, overlapping meshes, or non-manifold geometry can cause light leaks—bright spots where light escapes through tiny cracks.

To fix this:

• Use the Merge Actors tool to combine static meshes where possible.
• Check for gaps using the Show > Advanced > Light Complexity view mode. Bright red areas indicate potential leaks.
• Seal all openings in your level, especially around doors and windows.

Apply Correct Materials

Materials affect how light interacts with surfaces. A glossy floor will reflect more light than a matte one. Make sure your materials have realistic roughness, metallic, and normal map values.

Avoid using pure white or black materials unless intentional—they can cause extreme highlights or absorb too much light, throwing off your scene’s balance.

Adjusting Lightmass Settings for Better Quality

Lightmass is Unreal Engine’s global illumination system. It calculates how light bounces around your scene to create realistic lighting. Poor Lightmass settings are a common cause of dark, noisy, or unrealistic lighting.

Access Lightmass Settings

To adjust Lightmass:

1. Go to Window > World Settings.
2. Scroll down to the Lightmass section.
3. Expand the settings to see options like Indirect Lighting Quality, Indirect Lighting Smoothness, and Num Indirect Lighting Bounces.

Key Lightmass Settings to Tweak

Here are the most important settings to adjust:

• Indirect Lighting Quality: Controls the resolution of indirect lighting. Higher values reduce noise but increase bake time. Start with 2–4 for testing, then go up to 8–12 for final builds.
• Indirect Lighting Smoothness: Blurs indirect lighting to reduce noise. A value of 0.8–1.0 works well for most scenes.
• Num Indirect Lighting Bounces: Determines how many times light bounces. More bounces mean more realistic lighting but longer bake times. Use 2–4 for most scenes.
• Environment Intensity: Adjusts the brightness of the sky light. Increase this if your scene feels too dark outdoors.
• Static Lighting Level Scale: Affects the resolution of lightmaps. Lower values (like 0.5) increase detail but cost more. Use 1.0 for balanced quality.

Pro Tip: Always test lighting changes in a small section of your level before applying them globally. This saves time and helps you fine-tune settings.

Fixing Common Lighting Problems

Even with the best setup, lighting issues can still occur. Here’s how to diagnose and fix the most common problems.

Dark or Black Areas

If parts of your scene are too dark or completely black, it’s usually due to insufficient light or incorrect lightmap resolution.

Solutions:

• Add more light sources, especially sky lights or directional lights for outdoor scenes.
• Increase Lightmap Resolution on dark objects. Select the mesh, go to Details > Lighting, and raise the Light Map Resolution (try 64–128 for small objects, 32–64 for large ones).
• Ensure your sky light is set to Real Time Capture or has a high Cubemap Resolution.

Flickering or Noisy Shadows

Flickering shadows, especially in motion, are often caused by low lightmap resolution or insufficient Lightmass quality.

How to fix it:

• Increase Indirect Lighting Quality in Lightmass settings.
• Raise the Lightmap Resolution on affected meshes.
• Use Stationary lights instead of Movable if possible—they produce smoother shadows.
• Enable Contact Shadows in the light’s settings for sharper, more stable shadows on small details.

Light Leaks

Light leaks appear as bright streaks or spots where light escapes through gaps in geometry. They’re common around doors, windows, or seams between walls.

To fix light leaks:

• Seal all gaps in your level geometry.
• Use the Show > Advanced > Light Complexity view mode to locate leaks (red areas).
• Adjust the Lightmap Density view mode to see if lightmaps are too low-res.
• Consider using Lightmass Importance Volume to focus lighting calculations on key areas.

Overly Bright or Washed-Out Lighting

If your scene looks too bright or flat, it might be due to excessive light intensity or lack of contrast.

Try these fixes:

• Reduce the Intensity of your lights. Start with values between 500–2000 lumens for indoor lights.
• Adjust the Exposure in your post-process volume. Lower the Min Brightness and raise the Max Brightness to increase contrast.
• Use IES Profiles to simulate real-world light falloff and create more natural lighting patterns.

Using Light Propagation Volume (LPV) for Dynamic Lighting

For large, open worlds with moving lights, Light Propagation Volume (LPV) can provide dynamic global illumination without the cost of fully baked lighting.

When to Use LPV

LPV is ideal for:

• Outdoor environments with moving characters or vehicles.
• Scenes where lighting changes frequently.
• Games targeting mid-to-high-end hardware.

How to Enable LPV

To set up LPV:

1. Go to Project Settings > Rendering > Lighting.
2. Enable Light Propagation Volume.
3. Place an LPV Volume in your level (found under Volumes in the Modes panel).
4. Adjust the volume to cover your playable area.

Note: LPV can be performance-heavy. Use it only when necessary and test on target hardware.

Optimizing Lighting for Performance

Great lighting shouldn’t come at the cost of performance. Here’s how to keep your scenes running smoothly.

Reduce Light Count

Each light adds to the rendering cost. Use as few lights as possible:

• Combine multiple small lights into one larger one.
• Use emissive materials instead of lights for glowing objects (e.g., screens, signs).
• Disable lights that aren’t visible to the player.

Use Light Culling

Enable Light Culling in your project settings to prevent lights from affecting distant objects. This reduces unnecessary calculations.

Optimize Lightmap Resolution

High lightmap resolution looks great but uses more memory. Balance quality and performance:

• Use lower resolution (16–32) for large, distant objects.
• Use higher resolution (64–128) for close-up, detailed meshes.
• Avoid going above 256 unless absolutely necessary.

Use HLOD (Hierarchical Level of Detail)

HLOD combines distant objects into simplified meshes, reducing draw calls and improving performance. This also helps with lighting consistency at a distance.

Debugging Lighting with Visualization Tools

Unreal Engine includes powerful tools to help you debug lighting issues.

Lighting Visualization Modes

Access these via Show > Visualize in the viewport:

• Light Complexity: Shows how many lights affect each pixel. Red areas may indicate over-lighting.
• Lightmap Density: Displays lightmap resolution. Blue is good, red means too low.
• Stationary Light Overlap: Highlights areas where stationary lights overlap, which can cause performance issues.
• Reflection Environment: Helps check how reflections interact with lighting.

Use the Stat Unit Command

Type stat unit in the console to see real-time performance stats. Look for high GPU or Render times, which may indicate lighting bottlenecks.

Rebuilding Lighting: The Final Step

After making any lighting changes, you must rebuild lighting to see the results.

How to Rebuild Lighting

To rebuild:

1. Click the Build button in the toolbar (or press Ctrl+Shift+;).
2. Select Build Lighting Only to save time.
3. Wait for the process to complete—this can take from seconds to hours, depending on scene complexity.

Tip: Use Build All only when necessary. For quick iterations, rebuild lighting only.

Troubleshooting Common Lighting Errors

Even experienced developers run into lighting issues. Here’s how to solve them.

“Lighting Not Built” Warning

If you see this warning, it means lighting hasn’t been rebuilt. Simply click Build to fix it.

Missing or Incorrect Shadows

Shadows may disappear if:

• The object isn’t set to Cast Shadow in its details panel.
• The light’s Cast Shadows option is disabled.
• The light is too far from the object.

Check these settings and rebuild lighting.

Lighting Looks Different in Packaged Build

Sometimes lighting appears correct in the editor but wrong in a packaged game. This is often due to:

• Different Lightmass settings in the build.
• Missing sky light or post-process volume in the final level.
• Incorrect scalability settings.

Always test your final build on target hardware.

Conclusion

Fixing lighting in Unreal Engine 4 doesn’t have to be frustrating. By understanding light types, adjusting Lightmass settings, and using the right tools, you can create beautiful, realistic scenes that perform well. Remember to rebuild lighting after every change, optimize for performance, and use visualization tools to spot issues early.

With practice, you’ll develop an eye for lighting and be able to troubleshoot problems quickly. Whether you’re building a horror game, a sunny landscape, or a futuristic city, great lighting will bring your vision to life.