Unity3D研究院之LWRP中计算准确overdraw（一百一十）

using System.Collections.Generic;
#if UNITY_EDITOR
using UnityEditor;
using UnityEditor.Rendering.LWRP;
#endif
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.LWRP;

[CreateAssetMenu(fileName = "OverDrawRendererData", menuName = "Renderering/OverDrawRendererData", order = 2)]
public class OverDrawRendererData : ScriptableRendererData
{
    [SerializeField]
    private Material m_OverDrawQuad;
    [SerializeField]
    private Material m_OverDrawTransparent;


    public Material overDrawQuad => m_OverDrawQuad;
    public Material overDrawTransparent => m_OverDrawTransparent;

    protected override ScriptableRenderer Create()
    {
        return new OverDrawRenderer(this);
    }
}

public class OverDrawRenderer : ScriptableRenderer
{
    private OverDrawRenderPass m_OverDrawRenderQuadPass;
    private OverDrawRenderPass m_OverDrawRenderTransparentPass;
    public OverDrawRenderer(ScriptableRendererData data) : base(data)
    {
        m_OverDrawRenderQuadPass = new OverDrawRenderPass(SortingCriteria.CommonOpaque, RenderQueueRange.opaque,(data as OverDrawRendererData).overDrawQuad);
        m_OverDrawRenderTransparentPass = new OverDrawRenderPass(SortingCriteria.CommonTransparent, RenderQueueRange.transparent, (data as OverDrawRendererData).overDrawTransparent);
    }
    public override void Setup(ScriptableRenderContext context, ref RenderingData renderingData)
    {
            //绘制不透明物体overdraw
            EnqueuePass(m_OverDrawRenderQuadPass);
            //绘制半透明物体overdraw
            EnqueuePass(m_OverDrawRenderTransparentPass);
    }
}

public class OverDrawRenderPass : ScriptableRenderPass
{
    private SortingCriteria m_Criteria;
    private Material m_OverDrawMaterial;
    private FilteringSettings m_FilteringSettings;
    private RenderStateBlock  m_RenderStateBlock;
    private List<ShaderTagId> m_ShaderTagIds = new List<ShaderTagId>()
    {
        new ShaderTagId("SRPDefaultUnlit"),
        new ShaderTagId("LightweightForward"),
    };
    public OverDrawRenderPass(SortingCriteria criteria, RenderQueueRange renderQueueRange, Material overdrawMaterial)
    {
        this.m_Criteria = criteria;
        this.m_OverDrawMaterial = overdrawMaterial;
        this.m_FilteringSettings = new FilteringSettings(renderQueueRange);
        this.m_RenderStateBlock = new RenderStateBlock(RenderStateMask.Nothing);
        
    }
    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
        var drawingSettings = CreateDrawingSettings(m_ShaderTagIds, ref renderingData, this.m_Criteria);
        if(!renderingData.cameraData.isSceneViewCamera)
            drawingSettings.overrideMaterial = m_OverDrawMaterial;
        CommandBuffer cmd = CommandBufferPool.Get("Name");
        using(new ProfilingSample(cmd, "Name"))
        {
            context.ExecuteCommandBuffer(cmd);
            cmd.Clear();
            context.DrawRenderers(renderingData.cullResults, ref drawingSettings, ref m_FilteringSettings, ref m_RenderStateBlock);
        }
        context.ExecuteCommandBuffer(cmd);
        CommandBufferPool.Release(cmd);
    }
}
#if UNITY_EDITOR
[CustomEditor(typeof(OverDrawRendererData))]
public class OverDrawRendererDataEditor : ScriptableRendererDataEditor
{
    public override void OnInspectorGUI()
    {

        serializedObject.Update();
        EditorGUILayout.PropertyField(serializedObject.FindProperty("m_OverDrawQuad"));
        EditorGUILayout.PropertyField(serializedObject.FindProperty("m_OverDrawTransparent"));
        serializedObject.ApplyModifiedProperties();
        base.OnInspectorGUI();
    }
}
#endif

void LateUpdate()
{
   //不渲染overdraw
    ResetOverDrawShader();
    m_Camera.targetTexture = m_RT;
    m_Camera.Render();
    RenderTexture.active = m_RT;
    
    Texture2D texture2 = new Texture2D(m_RT.width, m_RT.height, TextureFormat.RGBA32, false);
    texture2.ReadPixels(new Rect(0, 0, m_RT.width, m_RT.height), 0, 0);
    //texture2就是不渲染overdraw物体的像素信息。


    //开始渲染overdraw
    SetOverDrawShader();
    m_Camera.targetTexture = m_RT;
    m_Camera.Render();
    RenderTexture.active = m_RT;
    Texture2D texture = new Texture2D(m_RT.width, m_RT.height, TextureFormat.RGBA32, false);
    texture.ReadPixels(new Rect(0, 0, m_RT.width, m_RT.height), 0, 0);
    //texture就是不渲染overdraw物体的像素信息。

    //最后通过遍历texture和texture2的像素值就能计算出来数据
}

        void ResetCamera()
        {
            if(SceneView.lastActiveSceneView)
                SceneView.lastActiveSceneView.AlignViewToObject(script.transform);
        }

Tools.visibleLayers = m_Camera.cullingMask = LayerMask.GetMask("TransparentFX");