Don’t worry, we’ve all been there and we’ve all panicked the first time.
URP or HDRP to Built-in Conversion
The solution is surprisingly simple. First navigate to the materials folder and select all the broken materials and in inspector set the shader to Standard or Standard (Specular setup).
After that all your materials should become visible.
Depending on the original materials, it is best to have a quick look over them, to check if some of them need to be changed to either Standard or Standard (Specular setup). You can do that by checking if they have a missing Specular or Metallic map and you can switch back and forth to see the difference. The other map will connect automatically if it is supposed to be there.
Transparent or Cutout Materials
Some materials Rendering mode might have to be changed from opaque to transparent.
And some need to be switched to Cutout.
If there are particle materials and the particles just look like squares, you need to find the material attached to the particle system and change it to a particle material (e.g. Particles/Standard Unlit) and attach a texture if necessary to the Albedo map.
With these steps you should have your scene converted to Built in RP in no time!
Check our Socials