Q. After migrating to URP, all assets and materials on the scene have become bright pink (magenta). Is it broken?

A. Please rest assured that it is not broken. This is a situation where Unity warns you that "An outdated shader is being used that is incompatible with the current graphics pipeline (URP)."

Failure symptoms and meaning of pink coloring

When migrating a Unity project from the conventional "Built-in Render Pipeline" to the "Universal Render Pipeline (URP)", an issue occurs where the entire screen or specific 3D models turn bright pink. This does not mean that the asset's 3D mesh or texture data itself is corrupted. The engine that renders the game is unable to decipher the drawing instruction program called the "shader" set for the material, and the error message is "We are displaying this color as an error because we do not know how to draw it."

An analogy for beginners: IH kitchen and clay pot recipes

Let's compare this situation to cooking and the kitchen.

The standard development environment up until now is the ``kitchen with a gas stove'' that has been popular for many years. The existing materials there were written according to the ``Recipe for Cooking Rice in a Clay Pot (Standard Shader)''.

The fact that we moved the project to URP this time means that we renovated the kitchen into a "state-of-the-art flat IH system kitchen (URP environment)." Even if you bring an old clay pot recipe to this modern IH kitchen and instruct the cook to ``cook some rice,'' the IH stove will not be able to heat the rice because it is not compatible with clay pots, resulting in an error. When an IH stove flashes an error light saying "This recipe cannot be used!", this is the material's pure pink display.

In order to solve this problem, you need to rewrite (convert) the recipes to "IH-specific recipes (URP/Lit shader, etc.)" that are compatible with the latest IH kitchens.

Main causes of bright pink

There are three reasons why materials may cause errors in the URP environment:

  1. Shader language and structure mismatch: The built-in Standard shader relies on older shader language descriptions (Cg language) and libraries. On the other hand, since URP uses the HLSL language and a dedicated library, shaders with old descriptions cannot be compiled and will result in an error.
  2. Missing URP asset settings: If you have just installed URP in a project, but the "URP Asset" that describes the URP operation settings is not registered in Unity's project settings (Project Settings > Graphics), the renderer will cause an error.
  3. Custom shaders or old shaders from the Asset Store: Old 3D models purchased from the Asset Store or custom shaders you've written yourself in the past are often not covered by the automatic conversion feature and are left behind as pink.

Step-by-step solution

Specific steps to make old materials compatible with URP.

Step 1: Back up the entire project (most important)

Before performing batch automatic conversion of materials, be sure to take a backup of the current state. The automatic conversion process is irreversible, to avoid the risk of some custom materials being irreversibly overwritten with unintended settings.

Step 2: Start Render Pipeline Converter

Select **`Window > Rendering > Render Pipeline Converter`** from the menu at the top of the Unity editor to open the converter window. This is a tool included in the latest Unity that automatically converts materials and project settings.

Step 3: Setting and executing conversion items

  • Select **`Built-in to URP`** from the drop-down menu at the top of the converter.
  • Check **`Material Upgrade`** in the list of conversion options.
  • Click the **`Initialize Converters`** button at the bottom of the window. This will scan your project and list the materials that need to be converted.
  • Check the list and if you are happy with it, click the **`Convert Assets`** button to execute it. The shader will be automatically rewritten to `URP/Lit` or `URP/Simple Lit`, the pink display will disappear and it will return to normal.

Troubleshooting and response flow

Problem you are experiencing Possible cause Specific countermeasures
Some materials remain pink after conversion Special shaders from the asset store and homemade shaders. Select the material manually and change the Shader to `Universal Render Pipeline/Lit` etc.
UI and sprites become pink A 3D shader is assigned to a 2D material. Reset Shader to `Universal Render Pipeline/2D/Sprite-Lit-Default` etc.

The following is a debug script that scans the material in the project for pink status while the game is running, and automatically replaces it with a dummy URP compatible shader. 

using UnityEngine;

public class URPMaterialChecker : MonoBehaviour
{
    public void ScanAndFixPinkMaterials()
    {
        Renderer[] renderers = FindObjectsOfType<Renderer>();
        Shader urpLitShader = Shader.Find("Universal Render Pipeline/Lit");

        if (urpLitShader == null) return;

        foreach (Renderer ren in renderers)
        {
            foreach (Material mat in ren.sharedMaterials)
            {
                if (mat == null) continue;

                if (mat.shader.name == "Hidden/InternalErrorShader" || 
                    mat.shader.name.Contains("Error"))
                {
                    mat.shader = urpLitShader;
                }
            }
        }
    }
}

By using these troubleshooting steps and diagnostic scripts, you can calmly resolve the ``alleged asset corruption'', which is a major hurdle during the transition period, and smoothly transition to a high-quality, high-performance drawing environment provided by the latest URP. Let's start by running the converter to normalize the graphics function.