> For the complete documentation index, see [llms.txt](https://frostember-studios.gitbook.io/trailbound/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://frostember-studios.gitbook.io/trailbound/getting-started/urp-and-hdrp.md).

# URP and HDRP

Pipeline-specific materials, shader channels, import steps and demo setup.

The main package contains the URP materials and demos. A separate supplied HDRP import package provides native HDRP materials, a Lit Shader Graph, volume/pipeline settings and matching versions of all four scenes. C# vehicle and soil behavior is shared between both pipelines.

### URP

1. Use a URP project and let Universal RP 17.0.4 import.
2. Import the main package. Open DeveloperLab or ForestRun through Workshop.
3. Add all four scenes to your build-scene list if you want runtime navigation.
4. For your own scene, use the shader `Frostember/Trailbound/Surface` and your own URP pipeline. Keep GPU instancing enabled on repeated vegetation.

### HDRP

1. Use an HDRP project. Complete Unity's HDRP setup for that project if needed.
2. Import the main package, then double-click `Compatibility/Trailbound_HDRP_1.0.0.unitypackage` inside the Project view.
3. Import the patch's supplied assets. It replaces only Trailbound's materials and four demo scenes, retaining their GUIDs and prefab references. Back up any personal edits to those supplied assets before replacing them.
4. Open DeveloperLab or ForestRun. The demo uses its native HDRP pipeline and Gradient Sky, exposure and colour-grade volume. Add all four scenes to your build-scene list for runtime navigation.
5. For your own materials, use `Frostember/Trailbound/Surface HDRP`. The optional menu **Tools > Frostember > Trailbound > HDRP > Apply supplied art materials** converts materials only under Trailbound/Materials and preserves baked maps and the supplied surface/wind values. It does not convert arbitrary project assets.

HDRP uses native Lit shading for the art and mud particles. Demo TextMesh labels use the supplied native Unlit Shader Graph: the font atlas supplies alpha coverage while each label retains its authored colour. Atlas RGB does not darken the text. Wind is evaluated consistently in lit, depth and shadow passes through the graph's vertex stage. Rooted tree wind, grass bending, bark/wood grain and soil wetness use the same stored mesh channels and material controls as URP.

### Mesh and material contracts

| Data                  | Meaning                                                      |
| --------------------- | ------------------------------------------------------------ |
| Vertex RGB            | Authored surface colours                                     |
| Soil vertex alpha     | Bearing hardness; visual wetness is independent              |
| Soil UV2              | Wetness and deformation/compression                          |
| Tree UV3              | Rooted wind height/weight                                    |
| Base map / normal map | Baked colour and continuous surface detail                   |
| Mask R / G            | Metallic / roughness (not HDRP's default packed mask layout) |

The supplied graph deliberately reads the same Trailbound mask convention as the URP shader. Do not substitute the mask directly into an unrelated HDRP Lit material and expect identical roughness. Shared shader-property names let the conversion preserve those values.

### Switching and extending

Use separate project copies when comparing pipelines. Re-import the main package's materials/scenes to return the supplied assets to URP. The HDRP archive remains optional and is not opened automatically. Project-wide pipeline/input/layer settings belong to your project. Built-in RP is not supported by this release.

The runtime screenshot helper uses Core RP's `RenderPipeline.StandardRequest`, so it can render through either active pipeline without a URP runtime dependency. Pipeline authoring assemblies use package version defines; installed packages determine which tools compile.