Adapt selection picker to URP

[thomas-tu]

Purpose of this PR

This PR updates the picking system so it properly runs on URP. We used to use an old hack in URP project: the picking system would force the BiRP to run temporarly to render the lookup texture. This is no longer something we can do due to some others packages that could react to the change of RP asset changes (example: VFX graph).

To solve this and since URP now allows render pass injection, I've created our own URP render pass and inject it when we run the picking system. URP uses HLSL so I had to migrate our CG shaders to HLSL.

Manually tested.

Links

Jira: UUM-133859

[u-pr]

PR Reviewer Guide 🔍

(Review updated until commit 9ac07b4)

Here are some key observations to aid the review process:

🎫 Ticket compliance analysis 🔶 UUM-133859 - Partially compliant Compliant requirements: Avoid render pipeline asset switching side-effects during selection picking URP picking path is implemented (URP render pass injection) instead of forcing BiRP for lookup rendering Non-compliant requirements: (empty) Requires further human verification: Verify the exact repro steps no longer show the VFX Graph compilation popup on the affected Unity versions/devices listed in the ticket Confirm no regressions for selection picking behavior across Face/Edge/Vertex modes in URP projects (manual/editor validation)

⏱️ Estimated effort to review: 4 🔵🔵🔵🔵⚪ The PR adds a new URP renderer path, new shaders, and modifies assembly references, which requires careful cross-platform/editor-vs-player and SRP-compatibility validation.

🏅 Score: 72 The overall approach matches the ticket intent, but there are high-risk integration issues (editor-only API in runtime code and URP selection detection) that can cause build breaks or incorrect renderer selection.

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Build Break The runtime assembly code imports UnityEditor, which will fail player builds whenever the file is compiled (e.g., URP package installed / PB_URP_MODE defined). Move editor-only code behind #if UNITY_EDITOR (or into an editor assembly) and keep the runtime implementation free of UnityEditor dependencies. using UnityEditor; using UnityEngine.Rendering; #if PB_URP_MODE using UnityEngine.Rendering.Universal; using UObject = UnityEngine.Object; using static UnityEngine.Rendering.RenderPipeline; #endif Hard Dependency The asmdef now hard-references Unity.RenderPipelines.Universal.Runtime; if that assembly is not present in some projects/environments, compilation will fail even when ProBuilder URP codepaths are not used. Consider isolating URP-specific code into a separate asmdef with define constraints (or other conditional assembly strategy) to avoid forcing URP as a dependency. "references": [ "Unity.ProBuilder.Poly2Tri", "Unity.ProBuilder.KdTree", "Unity.RenderPipelines.HighDefinition.Runtime", "Unity.RenderPipelines.Universal.Runtime", "Unity.RenderPipelines.Core.Runtime" ], Wrong Pipeline Check ShouldUseURP() returns true purely based on PB_URP_MODE (package presence), which can select the URP picker renderer even when the active render pipeline is not URP (e.g., project has URP installed but uses Built-in or HDRP). This can route picking through the wrong renderer and break selection. Prefer checking the active pipeline asset/type at runtime (e.g., GraphicsSettings.currentRenderPipeline is URP) rather than only a compile-time define. static bool ShouldUseURP() { #if PB_URP_MODE return true; #else return false; #endif

Update review

---

🤖 Helpful? Please react with 👍/👎 | Questions❓Please reach out in Slack #ask-u-pr

[u-pr]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Fix shader name mismatch Make the URP face picker shader identifier consistent with the actual shader name to prevent Shader.Find/material creation from failing. The added URP shader file declares Hidden/ProBuilder/FacePickerURP, so use that here as well. Runtime/Core/BuiltinMaterials.cs [73-75] static string k_EdgePickerShader = "Hidden/ProBuilder/EdgePickerURP"; static string k_VertexPickerShader = "Hidden/ProBuilder/VertexPickerURP"; -static string k_FacePickerShader = "Shader Graphs/FacePickerURP"; +static string k_FacePickerShader = "Hidden/ProBuilder/FacePickerURP"; Suggestion importance[1-10]: 9 __ Why: The k_FacePickerShader variable is assigned a path ("Shader Graphs/FacePickerURP") that does not match the actual shader name defined in FacePickerURP.shader ("Hidden/ProBuilder/FacePickerURP"). This discrepancy will cause the shader lookup to fail at runtime, breaking the face picking functionality when using URP.	High
	Always clean up temporary rendering resources Ensure render pipeline event unsubscription and temporary resource cleanup happen even if rendering/reading pixels throws. Wrap the render request + readback in a try/finally that always restores RenderTexture.active, releases rt, unsubscribes, and destroys the temporary camera object. Runtime/Core/SelectionPickerRendererURP.cs [97-116] +RenderTexture prev = RenderTexture.active; RenderPipelineManager.beginCameraRendering += CustomRenderPass; -if (RenderPipeline.SupportsRenderRequest(renderCam, request) == false) - Debug.LogWarning("RenderRequest not supported."); +try +{ + if (RenderPipeline.SupportsRenderRequest(renderCam, request) == false) + Debug.LogWarning("RenderRequest not supported."); -RenderPipeline.SubmitRenderRequest<StandardRequest>(renderCam, request); -RenderTexture prev = RenderTexture.active; -RenderTexture.active = rt; + RenderPipeline.SubmitRenderRequest<StandardRequest>(renderCam, request); -Texture2D img = new Texture2D(_width, _height, textureFormat, false, false); -img.ReadPixels(new Rect(0, 0, _width, _height), 0, 0); -img.Apply(); + RenderTexture.active = rt; -RenderTexture.active = prev; -RenderTexture.ReleaseTemporary(rt); -RenderPipelineManager.beginCameraRendering -= CustomRenderPass; -temporaryCamera = null; -UObject.DestroyImmediate(go); + Texture2D img = new Texture2D(_width, _height, textureFormat, false, false); + img.ReadPixels(new Rect(0, 0, _width, _height), 0, 0); + img.Apply(); -return img; + return img; +} +finally +{ + RenderTexture.active = prev; + RenderTexture.ReleaseTemporary(rt); + RenderPipelineManager.beginCameraRendering -= CustomRenderPass; + temporaryCamera = null; + UObject.DestroyImmediate(go); +} Suggestion importance[1-10]: 7 __ Why: Implementing a try/finally block ensures that resources such as the temporary RenderTexture are released, event subscriptions are removed, and the temporary GameObject is destroyed even if an exception occurs during the rendering or pixel reading process. This enhances the robustness of the selection picking logic.	Medium
More suggestions

---

🤖 Helpful? Please react with 👍/👎 | Questions❓Please reach out in Slack #ask-u-pr

[codecov-github-com]

Codecov Report

Attention: Patch coverage is 37.50000% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
Editor/EditorCore/EditorSceneViewPicker.cs	0.00%	12 Missing ⚠️
Runtime/Core/SelectionPickerRendererURP.cs	0.00%	3 Missing ⚠️

@@            Coverage Diff             @@
##           master     #657      +/-   ##
==========================================
+ Coverage   36.05%   36.98%   +0.92%     
==========================================
  Files         277      278       +1     
  Lines       34909    35018     +109     
==========================================
+ Hits        12588    12951     +363     
+ Misses      22321    22067     -254     

Flag	Coverage Δ
probuilder_MacOS_6000.0	35.58% <37.50%> (+1.00%)	⬆️
probuilder_MacOS_6000.3	35.58% <37.50%> (+1.00%)	⬆️
probuilder_MacOS_6000.4	35.57% <37.50%> (+1.00%)	⬆️
probuilder_MacOS_6000.5	35.58% <37.50%> (+1.00%)	⬆️
probuilder_MacOS_6000.6	35.58% <37.50%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
Runtime/Core/BuiltinMaterials.cs	52.42% <100.00%> (ø)
Runtime/Core/SelectionPickerRenderer.cs	92.72% <100.00%> (+0.05%)	⬆️
Runtime/Core/SelectionPickerRendererURP.cs	0.00% <0.00%> (ø)
Editor/EditorCore/EditorSceneViewPicker.cs	49.16% <0.00%> (-1.01%)	⬇️

... and 47 files with indirect coverage changes

ℹ️ Need help interpreting these results?

[unity-kristinn]

/test_plan

[u-pr]

Test Plan

• Test plan approved by PR author
• Test execution in progress
• Test execution complete
• Ready for merge

---

Summary of Changes & Risk Assessment

Summary of Changes

This PR transitions the ProBuilder selection picking system to a native URP implementation. It replaces a legacy "pipeline-switching" hack with a dedicated ScriptableRenderPass using the RenderGraph API and migrates picking shaders from CG to HLSL (ProBuilderCG_URP.hlsl). It also introduces SelectionPickerRendererURP to handle the rendering of lookup textures within the Universal Render Pipeline context.

Risk Assessment

• High Risk Areas:
  • Shader/Material Resolution: Potential null references if k_FacePickerShader name mismatch identified in PR comments isn't resolved in BuiltinMaterials.cs:L75.
  • Resource Management: Risk of GameObject or RenderTexture leaks in SelectionPickerRendererURP.cs if an exception occurs during ReadPixels, as cleanup logic is not currently in a try/finally block.
• Medium Risk Areas:
  • Cross-Pipeline Compatibility: Ensuring the picking system still functions correctly in Built-in (BiRP) and HDRP after the logic branch changes in SelectionPickerRenderer.cs:L169.
  • Asmdef Dependencies: New hard references to URP/HDRP runtime assemblies in Unity.ProBuilder.asmdef could cause compilation errors in projects missing those packages if not properly guarded.
• Low Risk Areas: Changelog accuracy and basic UI selection workflows.

---

Test Scenarios

Functional Testing

• URP Selection Verification: In a URP project, verify that Vertex, Edge, and Face selection modes work correctly on a ProBuilder mesh.
• Marquee/Rect Selection: Perform a rectangle selection in the Scene View and verify that it no longer triggers a script recompilation (the core fix for UUM-133859).
• Shader Loading: Verify that BuiltinMaterials.Init() correctly finds the new HLSL shaders (especially the Face Picker) without "Shader not found" errors in the console.

Regression Testing

• Built-in Pipeline (BiRP) Parity: Open a project using BiRP and verify that selection picking remains functional and hasn't regressed due to the logic changes in SelectionPickerRenderer.cs.
• HDRP Verification: Ensure picking still works in HDRP projects, as the initialization logic for SelectionPickerRendererHDRP was modified in SelectionPickerRenderer.cs:L168.
• Dependency Guarding: Verify that the package compiles in a minimal Unity project that does not have the URP or HDRP packages installed.

🔍 Regression Deep Dive (additional risks identified)

• Camera Modes: Test selection using an Orthographic camera in URP to validate the offset logic in ProBuilderCG_URP.hlsl:L36.
• Leak Detection: Monitor the Hierarchy during repeated selection actions in URP to ensure the temporary "New Game Object" created in SelectionPickerRendererURP is destroyed properly every time.
• Z-Fighting/Offset: Verify that edge selection doesn't suffer from excessive flickering or depth-testing issues in URP compared to BiRP.

Edge Cases

• Resolution Extremes: Test selection picking in a very small Scene View window and a 4K resolution window to ensure ReadPixels coordinates in SelectionPickerRendererURP.cs are accurate.
• Mixed Shaders: Test selection on a ProBuilder mesh that uses a custom Shader Graph material to ensure the picker pass still identifies the geometry.

---

_{💡 This test plan updates automatically when /test_plan is run on new commits. If you have any feedback, please reach out in #ai-qa}

---

🤖 Helpful? Please react with 👍/👎 | Questions❓Please reach out in Slack #ask-u-pr

[unity-kristinn]

I could not box select anymore.

i tried the repro steps of UUM-133859. I cannot box select anymore. Is this expected?

Screen.Recording.2026-03-09.at.14.09.52.mov

[u-pr]

Persistent review updated to latest commit 9ac07b4

[thomas-tu]

LGTM! I'm not able to approve my own PR, @lopezt-unity, I give your changes a 🍏

[thomas-tu]

This could be removed

[lopezt-unity]

LGTM, mu changes were 🍏 by @thomas-tu.