Lighting doesn't work in Unity with built-in URP: Unraveling the Mystery

Are you tired of struggling with lighting in Unity using the built-in Universal Render Pipeline (URP)? You’re not alone! Many developers have encountered this issue, and it’s time to shed some light (pun intended) on the matter. In this comprehensive guide, we’ll delve into the common causes, troubleshooting steps, and expert-level solutions to get your lighting working like a charm.

The Symptoms

Before we dive into the fix, let’s identify the symptoms. If you’re experiencing any of the following, you’re in the right place:

• Light sources are not emitting light
• Shadows are not being cast
• Lighting looks incorrect or inconsistent
• Scene is too bright or too dark

Common Causes

Now that we’ve established the symptoms, let’s explore the most common causes of lighting issues in Unity with URP:

1. Incorrect Lighting Settings

   URP uses a different lighting model than the built-in renderer. Make sure you’re using the correct settings for your lighting setup.

2. Missing or Incorrectly Configured Light Sources

   Double-check that your light sources are properly set up, and their properties are correctly configured.

3. Incorrect Shader or Material Settings

   URP-compatible shaders and materials are essential for proper lighting. Ensure you’re using the correct ones for your project.

4. Scene Hierarchy Issues

   A cluttered or disorganized scene hierarchy can cause lighting issues. Keep your scene organized, and avoid unnecessary nesting.

Troubleshooting Steps

Before we dive into the advanced solutions, let’s try some basic troubleshooting steps:

1. Check the Unity Version

   Ensure you’re running the latest version of Unity, as older versions might have known lighting issues.

2. Verify Lighting Settings

   Check the Lighting window (Window > Lighting > Settings) to ensure the correct settings are applied.

3. Light Source Inspection

   Inspect each light source, checking its type, range, and intensity. Adjust as needed.

4. Shader and Material Review

   Review your shaders and materials, ensuring they’re URP-compatible and correctly configured.

5. Scene Hierarchy Clean-up

   Organize your scene hierarchy, removing unnecessary objects and simplifying the structure.

Advanced Solutions

If the troubleshooting steps didn’t resolve the issue, it’s time to dive deeper:

LWRP and URP-Built-In Compatibility

If you’re using LWRP (Lightweight Render Pipeline) assets in a URP project, you might encounter compatibility issues. Try the following:

// Convert LWRP assets to URP-compatible assets
using UnityEngine.Rendering.Universal;

public class LWRPtoURPConverter : ScriptableRendererFeature
{
    [System.Serializable]
    public class LWRPtoURPConversionPass : ScriptableRenderPass
    {
        // ...
    }
}

Custom Lighting Shaders

Create a custom lighting shader to bypass URP’s built-in limitations. Here’s an example:

Shader "Custom/LightingShader"
{
    Properties
    {
        _MainTex ("Albedo (RGBA)", 2D) = "white" {}
        _MetallicGlossMap ("Metallic Gloss Map", 2D) = "white" {}
        _BumpMap ("Normal Map", 2D) = "bump" {}
    }

    SubShader
    {
        Tags {"Queue"="Transparent" "RenderType"="Transparent"}
        LOD 200

        CGPROGRAM
        #pragma surface surf Lambert

        struct Input
        {
            float2 uv_MainTex;
        };

        sampler2D _MainTex;
        sampler2D _MetallicGlossMap;
        sampler2D _BumpMap;

        void surf (Input IN, inout SurfaceOutput o)
        {
            fixed4 col = tex2D(_MainTex, IN.uv_MainTex) * _Color;
            o.Albedo = col.rgb;
            o.Alpha = col.a;
            o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_MainTex));
            return;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

Scene-Specific Solutions

In some cases, scene-specific solutions are necessary:

Issue	Solution
Shadows cast incorrectly	Adjust the light source’s shadow distance and bias
Lighting looks inconsistent	Check object orientations, and ensure correct Light Probe Group assignments
Scene is too bright or too dark	Adjust the Lighting window’s exposure and intensity settings

Conclusion

Lighting doesn’t work in Unity with built-in URP? Not anymore! By following this comprehensive guide, you should now have a solid understanding of the common causes, troubleshooting steps, and advanced solutions to get your lighting issues resolved. Remember to stay calm, patient, and methodical in your approach, and don’t hesitate to experiment and try new things.

Happy lighting, and happy coding!

Frequently Asked Question

Having trouble with lighting in Unity using the built-in Universal Render Pipeline (URP)? You’re not alone! Check out these FAQs to get your lighting back on track.