Unity URP custom grab pass

readme.md

Render Feature Setup

Get Global Texture in Blackboard

Sample Texture in Graph

Example Shader Graph to distort image

GrabScreenFeature.cs

using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class GrabScreenFeature : ScriptableRendererFeature
{
    [System.Serializable]
    public class Settings
    {
        public string TextureName = "_GrabPassTransparent";
        public LayerMask LayerMask;
    }

    class GrabPass : ScriptableRenderPass
    {
        RenderTargetHandle tempColorTarget;
        Settings settings;

        RenderTargetIdentifier cameraTarget;

        public GrabPass(Settings s)
        {
            settings = s;
            renderPassEvent = RenderPassEvent.AfterRenderingTransparents;
            tempColorTarget.Init(settings.TextureName);
        }

        public void Setup(RenderTargetIdentifier cameraTarget)
        {
            this.cameraTarget = cameraTarget;
        }

        public override void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescriptor)
        {
            cmd.GetTemporaryRT(tempColorTarget.id, cameraTextureDescriptor);
            cmd.SetGlobalTexture(settings.TextureName, tempColorTarget.Identifier());
        }

        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            CommandBuffer cmd = CommandBufferPool.Get();
            context.ExecuteCommandBuffer(cmd);
            cmd.Clear();

            Blit(cmd, cameraTarget, tempColorTarget.Identifier());

            context.ExecuteCommandBuffer(cmd);
            CommandBufferPool.Release(cmd);
        }

        public override void FrameCleanup(CommandBuffer cmd)
        {
            cmd.ReleaseTemporaryRT(tempColorTarget.id);
        }
    }

    class RenderPass : ScriptableRenderPass
    {
        Settings settings;
        List<ShaderTagId> m_ShaderTagIdList = new List<ShaderTagId>();

        FilteringSettings m_FilteringSettings;
        RenderStateBlock m_RenderStateBlock;

        public RenderPass(Settings settings)
        {
            this.settings = settings;
            renderPassEvent = RenderPassEvent.AfterRenderingTransparents + 1;

            m_ShaderTagIdList.Add(new ShaderTagId("SRPDefaultUnlit"));
            m_ShaderTagIdList.Add(new ShaderTagId("UniversalForward"));
            m_ShaderTagIdList.Add(new ShaderTagId("LightweightForward"));

            m_FilteringSettings = new FilteringSettings(RenderQueueRange.all, settings.LayerMask);
            m_RenderStateBlock = new RenderStateBlock(RenderStateMask.Nothing);
        }

        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            CommandBuffer cmd = CommandBufferPool.Get();

            context.ExecuteCommandBuffer(cmd);
            cmd.Clear();

            DrawingSettings drawSettings;
            drawSettings = CreateDrawingSettings(m_ShaderTagIdList, ref renderingData, SortingCriteria.CommonTransparent);
            context.DrawRenderers(renderingData.cullResults, ref drawSettings, ref m_FilteringSettings, ref m_RenderStateBlock);

            context.ExecuteCommandBuffer(cmd);
            CommandBufferPool.Release(cmd);
        }
    }

    GrabPass grabPass;
    RenderPass renderPass;
    [SerializeField] Settings settings;

    public override void Create()
    {
        grabPass = new GrabPass(settings);
        renderPass = new RenderPass(settings);
    }

    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        grabPass.Setup(renderer.cameraColorTarget);

        renderer.EnqueuePass(grabPass);
        renderer.EnqueuePass(renderPass);
    }
}

LICENSE

MIT License

Copyright (c) 2020 Refsa

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.