UI blur for HDRP

A real-time Kawase dual-filter blur for Unity UI, rendered as an HDRP Custom Pass.

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Requirements Install Setup Settings Sample in a UI shader Shaders URP vs. HDRP

com.bluecadet.uiblur-hdrp renders the same Kawase dual-filter blur as the URP package, integrated into the High Definition Render Pipeline through UIBlurCustomPass, a CustomPass added to a Custom Pass Volume. The implementation lives in one file, Scripts/UIBlurCustomPass.cs (namespace Bluecadet.UIBlur.HDRP).

Requirements

Unity 6000.3+
High Definition Render Pipeline (HDRP)

HEADS UP

package.json declares no dependency on HDRP. If HDRP isn’t installed in the consuming project, this package won’t compile.

Install

OpenUPM is the recommended path:

openupm add com.bluecadet.uiblur-hdrp

The scoped registry (https://package.openupm.com, scope com.bluecadet) only needs adding once per project.

To install from a Git URL instead, point at the release tag, which follows the com.bluecadet.uiblur-hdrp@<version> format:

json

{
  "dependencies": {
    "com.bluecadet.uiblur-hdrp": "https://github.com/bluecadet/unity-packages.git?path=Packages/com.bluecadet.uiblur-hdrp#com.bluecadet.uiblur-hdrp@<version>"
  }
}

Pick a version from Releases — every released tag is listed there. The openupm add form above always takes the latest.

Setup

Create an empty GameObject in your scene.
Add Component > Rendering > Custom Pass Volume.
Set its injection point to your preferred timing.
Click + and select UIBlurCustomPass.
Configure the settings below.

UIBlurCustomPass is [System.Serializable], but its Setup, Cleanup, and Execute overrides are all protected — there’s no public API beyond the three serialized fields below, and nothing to call from script.

Settings

Field	Range	Default	Description
`blurScale`	0–256	`4`	Blur intensity. Higher values produce stronger blur.
`renderTextureName`	string	`_UIBlurTexture`	Name of the global render texture that UI shaders sample.
`resolutionScale`	0.25–1.0	`0.5`	Render resolution multiplier, used as-is with no further clamping.

Unlike the URP inspector, these fields render without group headers — the [Header(...)] attributes in source are commented out.

NOTE

There’s no “Blur Passes” inspector setting. Pass count is computed at render time from blurScale via a private ComputeBlurParams, capped internally at 12 passes — it isn’t user-configurable.

Sample in a UI shader

hlsl

TEXTURE2D_X(_UIBlurTexture);
SAMPLER(sampler_UIBlurTexture);

half4 frag(Varyings i) : SV_Target {
    float2 screenUV = i.screenPos.xy / i.screenPos.w;
    half4 blurColor = SAMPLE_TEXTURE2D_X(_UIBlurTexture, sampler_UIBlurTexture, screenUV);
    return blurColor * _Color;
}

For the Kawase dual-filter algorithm itself, see the URP package.

Shaders

Asset	Shader name
`Shaders/KawaseDualFilter.shader`	`Bluecadet/UIBlur/KawaseDualFilterHDRP`
`Shaders/UIBlur.shader`	`Bluecadet/UIBlur/UIBlurHDRP`

URP vs. HDRP

	URP	HDRP
Integration	`UIBlurRenderFeature` on a URP Renderer asset	`UIBlurCustomPass` inside a Custom Pass Volume
Pass timing	Serialized `renderPassEvent`, default `AfterRenderingTransparents`	The Custom Pass Volume’s injection point — no field on the pass itself
Settings shape	Separate `BlurSettings` class, plus a `BlurScale` passthrough property	Three fields directly on the pass, no property wrappers
Internal pass cap	`MAX_PASSES = 6`	`MAX_PASSES = 12`
Resolution clamp	`Setup` re-clamps `resolutionScale` to `0.1–1`	Uses `resolutionScale` as-is
Render path	Render Graph (`Blitter.BlitTexture`)	`RTHandle` arrays + `CoreUtils.DrawFullScreen`
Blur shader	`Bluecadet/UIBlur/KawaseDualFilter`	`Bluecadet/UIBlur/KawaseDualFilterHDRP`
Example UI shader	`Bluecadet/UIBlur/UIBlur`	`Bluecadet/UIBlur/UIBlurHDRP`

The pipelines also differ internally: HDRP skips the render-graph abstraction in favor of manually pre-allocated RTHandle arrays (RTHandles.Alloc) drawn with CoreUtils.DrawFullScreen / CoreUtils.SetRenderTarget; its shaders use SAMPLE_TEXTURE2D_X/TEXTURE2D_X for XR single-pass and a manual UV Y-flip via UNITY_UV_STARTS_AT_TOP, and carry a "RenderPipeline" = "HDRenderPipeline" tag. In the Scene view (CameraType.SceneView), HDRP clears its final render target to Color.clear and sets that as the global texture, where URP swaps in a black texture instead.