手把手教你抄写URP——2——透明材质

参考的主要还是URP的代码，这里誊抄的主要目的是熟悉SRP的编写过程，最后完成一套框架。

参考地址：https://gitee.com/yichichunshui/srpframework.git
版本号：b733bdadf9c53b97f133d46d035375cc24a630a5

本节是SRPFramework的第2节。
具体完成如下的任务：
1、实现透明物体的绘制

创建透明shader：

Shader "Unlit/Transparent"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "Queue"="Transparent" "LightMode"="SRPRenderPipeline"}
        LOD 100
		Blend SrcAlpha OneMinusSrcAlpha
		ZWrite Off

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
				return fixed4(1,1,0,0.5f);
            }
            ENDCG
        }
    }
}

注意这里的queue设置为transpant。而不是renderType=Transparent，这里我遇到一个坑。

创建透明材质：

这里如果选择是From Shader，则一定要设置好Queue=Transparent。

在forwardrender中增加一个m_transparentPass：

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

public class ForwardRender : ScriptRenderBase
{
    public DrawObjectPass m_drawObjectPass;
    public DrawSkybox m_drawSkybox;
    public DrawObjectPass m_transparentPass;

    public ForwardRender()
    {
        m_drawObjectPass = new DrawObjectPass("Draw Opaque", SortingCriteria.CommonOpaque, RenderQueueRange.opaque);
        m_drawSkybox = new DrawSkybox();
        m_transparentPass = new DrawObjectPass("Draw Transparent", SortingCriteria.CommonTransparent, RenderQueueRange.transparent);
    }

    public override void Init(ScriptableRenderContext context, ref RenderData renderData)
    {
        AddPass(m_drawObjectPass);
        AddPass(m_drawSkybox);
        AddPass(m_transparentPass);
    }
}

重新写DrawObjectPass：

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

public class DrawObjectPass : RenderPassBase
{
    private List<ShaderTagId> m_drawShaderIDs;
    private FilteringSettings m_filterSettings;
    private DrawingSettings m_drawSettings;
    private SortingCriteria m_sortingCriteria;
    private RenderQueueRange m_renderQueueRange;
    private ProfilingSampler m_profilingSampler;


    public DrawObjectPass(string profileTag, SortingCriteria sortingCriteria, RenderQueueRange renderQueueRange)
    {
        m_sortingCriteria = sortingCriteria;
        m_renderQueueRange = renderQueueRange;
        m_drawShaderIDs = new List<ShaderTagId>();
        m_drawShaderIDs.Add(new ShaderTagId("SRPRenderPipeline"));
        //m_drawShaderIDs.Add(new ShaderTagId("SRPDefaultUnlit"));
        LayerMask layerMask = -1;
        m_filterSettings = new FilteringSettings(m_renderQueueRange, layerMask);
        m_profilingSampler = new ProfilingSampler(profileTag);
    }

    public override void Execute(ScriptableRenderContext context, ref RenderData renderData)
    {
        SortingSettings sortingSettings = new SortingSettings(renderData.m_cameraData.m_camera) { criteria = m_sortingCriteria };
        m_drawSettings = new DrawingSettings(m_drawShaderIDs[0], sortingSettings);
        for (int i = 1; i < m_drawShaderIDs.Count; ++i)
        {
            m_drawSettings.SetShaderPassName(i, m_drawShaderIDs[i]);
        }
        context.DrawRenderers(renderData.m_cullingResults, ref m_drawSettings, ref m_filterSettings);
    }
}

framedebugger中情况如下：

效果为：

黄色的球为透明的，z深度关闭写，帧调试器中绘制顺序正确，效果混合正确。