先整理一下原來透明怎么設定的

1.Build-in

獲取透明的Shader，修改模型材質的Shader，修改顏色引數透明度，修改材質是否為空

   /// <summary>
    /// 將游戲物體設定成透明的（包括子物體也都設定成透明的）
    /// </summary>
    /// <param name="go"></param>
    /// <param name="transparent"></param>
    /// <param name="color"></param>
    /// <param name="isSpecular"></param>
    /// <param name="removeTexture"></param>
    /// <returns></returns>
    public static bool SetTransparent(this GameObject go, Color color, bool isSpecular, bool removeTexture = false)
    {
        Renderer render = go.GetComponent<Renderer>();
        if (render == null) return false;

        Shader shader = ShaderHelper.GetTransparentShader(isSpecular);

        for (int i = 0; i < render.materials.Length; i++)
        {
            SetTransparentMaterial(render, i, shader, color, removeTexture);
            //StardardShaderSet.SetMaterialRenderingMode(mm, RenderingMode.Transparent);
        }
        return true;
    }

    /// <summary>
    /// 修改材質，達到透明的效果
    /// </summary>
    /// <param name="render"></param>
    /// <param name="i"></param>
    /// <param name="shader"></param>
    /// <param name="color"></param>
    /// <param name="removeTexture"></param>
    private static void SetTransparentMaterial(Renderer render, int i, Shader shader, Color color, bool removeTexture)
    {
        //Material mm = new Material(render.materials[i]);
        //Material mm = render.materials[i];
        //render.materials[i] = mm;
        render.materials[i].shader = shader;
        render.materials[i].color = color;
        if (removeTexture)
        {
            render.materials[i].mainTexture = null;
        }
    }

2.URP

修改URP/Lit材質的_SurfaceType，_Mode等引數，

參考：https://answers.unity.com/questions/1608815/change-surface-type-with-lwrp.html?_ga=2.257083661.724107984.1607480798-60239732.1590568025

using UnityEngine;
 using System;
 
 public class DisplayController : MonoBehaviour
 {
     public enum SurfaceType
     {
         Opaque,
         Transparent
     }
 public enum BlendMode
 {
     Alpha,
     Premultiply,
     Additive,
     Multiply
 }
 
 public Material wallMaterial;
 
 public void ChangeWallTransparency(bool transparent)
 {
     if (transparent)
     {
         wallMaterial.SetFloat("_Surface", (float)SurfaceType.Transparent);
         wallMaterial.SetFloat("_Blend", (float)BlendMode.Alpha);
     }
     else
     {
         wallMaterial.SetFloat("_Surface", (float)SurfaceType.Opaque);
     }
     SetupMaterialBlendMode(wallMaterial);
 }
 void SetupMaterialBlendMode(Material material)
 {
     if (material == null)
         throw new ArgumentNullException("material");
     bool alphaClip = material.GetFloat("_AlphaClip") == 1;
     if (alphaClip)
         material.EnableKeyword("_ALPHATEST_ON");
     else
         material.DisableKeyword("_ALPHATEST_ON");
     SurfaceType surfaceType = (SurfaceType)material.GetFloat("_Surface");
     if (surfaceType == 0)
     {
         material.SetOverrideTag("RenderType", "");
         material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
         material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
         material.SetInt("_ZWrite", 1);
         material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
         material.renderQueue = -1;
         material.SetShaderPassEnabled("ShadowCaster", true);
     }
     else
     {
         BlendMode blendMode = (BlendMode)material.GetFloat("_Blend");
         switch (blendMode)
         {
             case BlendMode.Alpha:
                 material.SetOverrideTag("RenderType", "Transparent");
                 material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
                 material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                 material.SetInt("_ZWrite", 0);
                 material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                 material.renderQueue = (int)UnityEngine.Rendering.RenderQueue.Transparent;
                 material.SetShaderPassEnabled("ShadowCaster", false);
                 break;
             case BlendMode.Premultiply:
                 material.SetOverrideTag("RenderType", "Transparent");
                 material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                 material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                 material.SetInt("_ZWrite", 0);
                 material.EnableKeyword("_ALPHAPREMULTIPLY_ON");
                 material.renderQueue = (int)UnityEngine.Rendering.RenderQueue.Transparent;
                 material.SetShaderPassEnabled("ShadowCaster", false);
                 break;
             case BlendMode.Additive:
                 material.SetOverrideTag("RenderType", "Transparent");
                 material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.One);
                 material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.One);
                 material.SetInt("_ZWrite", 0);
                 material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                 material.renderQueue = (int)UnityEngine.Rendering.RenderQueue.Transparent;
                 material.SetShaderPassEnabled("ShadowCaster", false);
                 break;
             case BlendMode.Multiply:
                 material.SetOverrideTag("RenderType", "Transparent");
                 material.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.DstColor);
                 material.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.Zero);
                 material.SetInt("_ZWrite", 0);
                 material.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                 material.renderQueue = (int)UnityEngine.Rendering.RenderQueue.Transparent;
                 material.SetShaderPassEnabled("ShadowCaster", false);
                 break;
         }
     }
 }
 }

3.HDRP

參考：https://forum.unity.com/threads/hdrp-make-surface-transparent-in-runtime.663025/#post-4439554

It seems like the proper thing to do is to have 2 materials, one opaque and one transparent, and switch materials on the mesh as needed.

根據查到的資料，運行程序中修改_SurfaceType，沒有效果，建議給模型設定一個透明的材質，切換材質來達到透明的效果，

測驗發現也可以使用將透明材質的屬性全部Copy過來，一樣能夠透明，需要將原材質的資訊備份（顏色、材質），Copy透明材質，還原原資訊，

                    var color=material.GetColor("_BaseColor");
                    var texture=material.GetTexture("_BaseColorMap");

                    if(Transparent_Mat==null){
                        Transparent_Mat=Resources.Load<Material>("HDRPLit_Transparent_Double");
                    }

                    if(EnableTransparent==true){
                        Material m=GameObject.Instantiate(Transparent_Mat);
                        material.CopyPropertiesFromMaterial(m);
                        material.SetColor("_BaseColor", color);
                        material.SetTexture("_BaseColorMap", texture);
                    }

由于歷史原因，專案中多處存在透明代碼，適用于不同的渲染關系，有空找個時間統一一下，寫一個統一處理三種情況的代碼，

4.公司相關代碼說明

TransparentHelper：最早的Build-in的透明功能

StartdarMaterialController:URP和HDRP的透明功能，呼叫StardarShaderMatHelper.SetMaterialRenderingMode

ModelChange：工藝流程的透明功能，呼叫StardarShaderMatHelper.SetMaterialRenderingMode