feat: Add MirrorRenderPipelineConverter for URP Compatibility

[MrGadget1024]

Overview

This pull request introduces MirrorRenderPipelineConverter, an editor script that automatically converts materials in the Assets/Mirror/Examples folder from Unity’s built-in render pipeline (e.g., Standard, Legacy Shaders) to the Universal Render Pipeline (URP) in Unity 6000+. It ensures Mirror Networking’s example scenes remain visually consistent and functional in modern URP projects, addressing the shift from the default built-in pipeline (Unity 2019) to URP in Unity 6000.

Key Features

• Automatic Conversion: Runs on project load, detects URP, and prompts with options: “Go Ahead” (convert), “Not Now” (skip), or “Don’t Ask Again” (set flag without converting).
• Targeted Scope: Only processes .mat files within Assets/Mirror/Examples and subfolders, preserving user project assets.
• Property Preservation: Transfers critical material properties:
  • Albedo color (_Color to _BaseColor)
  • Texture and tiling (_MainTex to _BaseMap, including _MainTex_ST)
  • Normal maps (_BumpMap)
  • Metallic and smoothness (_Metallic, _Glossiness to _Smoothness)
  • Transparency (render queue to _Surface)
  • Forward rendering options (_SpecularHighlights, _GlossyReflections to _EnvironmentReflections)
• Shader Handling: Forces conversion of incompatible shaders (Standard, Legacy Shaders/*) to URP/Lit, skips URP-compatible shaders (e.g., Skybox/6 Sided).
• Debugging Support: Extensive logging with clickable material references in the Console.

Motivation

Starting with Unity 6000, the built-in render pipeline is optional, and URP is the default. Without conversion, Mirror’s example materials (built for Unity 2019’s built-in pipeline) appear pink or incorrect in URP projects due to shader incompatibility. This script eliminates manual updates, ensuring a seamless experience for users upgrading to Unity 6000+.

Implementation Details

• Trigger: Uses [InitializeOnLoad] to check on project open, with a flag file (MirrorExamplesPipelineConverted.txt) to prevent re-prompting.
• Path Detection: Dynamically finds the Examples folder relative to the script’s location, accommodating user folder rearrangements.
• Robustness: Wraps conversion in a try-catch block, filters for .mat files, and validates shader availability.
• User Choice: Dialog respects user intent, with button order adjusted for intuitive UX (Go Ahead = left, Don’t Ask Again = right, Not Now = middle).

Impact

• User Experience: Examples work out of the box in URP, avoiding pink materials or manual fixes.
• Maintainability: Clear comments and logs simplify future tweaks or debugging.
• Compatibility: Supports Unity 6000+ URP projects while respecting built-in pipeline users.

Testing

• Validated in a fresh Unity 6000 URP 3D project with iterative imports:
  • Confirmed preservation of color, texture, tiling, transparency, and rendering options (e.g., Ground.mat, Robot_Color, Portal).
  • Verified settings like shininess by matching original _GlossyReflections and _SpecularHighlights settings.
• Logs provide material-specific feedback for verification.