【Unity3D】实现Decal贴花效果，模拟战旗游戏地形效果

一、基础版

二、Post Process 辉光Bloom效果 + 矩形渐隐

涉及知识点：Decal贴花、屏幕后处理Bloom、屏幕空间构建世界空间、ChracterController物体移动、Terrain地形创建

一、基础版

Unity 2019.4.0f1 普通渲染管线（非URP、非HDRP）
URP HDRP 在Unity 2021.2以上均可直接使用内置的贴花系统，具体网上有说明。

贴花物体是一个个Cube立方体，我将它拉长了Y轴便于能接触到地面。

其中角色物体胶囊体要进行设置渲染层级，GetComponent<MeshRenderer>().material.renderQueue = 3001; //将人物放到贴花物体之后渲染，不被贴花物体影响

如这个Cube长方体就是红色边缘的Cube贴花，贴花颜色是红色。

贴花物体是透明层，不写入深度和深度检测，以及裁剪正面，不裁剪背面。

可参考：贴花(Decal)效果在Shader里是如何实现的_哔哩哔哩_bilibili

核心代码是DepthToWorldPosition，屏幕空间反向构建世界空间，很类似全局雾效，注意摄像机要开启深度贴图。摄像机挂上这个如下脚本设置：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class OpenDepthTexture : MonoBehaviour
{public DepthTextureMode mode;private void Awake(){GetComponent<Camera>().depthTextureMode = mode;}
}

Shader "Unlit/SimpleDecal"
{Properties{_MainTex ("Texture", 2D) = "white" {}_Color ("Color", Color) = (1,1,1,1)}SubShader{Tags { "RenderType"="Transparent" "Queue"="Transparent" }LOD 100Pass{//Blend One DstAlphaBlend SrcAlpha OneMinusSrcAlpha//Blend One OneZWrite OffZTest OffCull Front 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;float4 screenPos : TEXCOORD3;};sampler2D _MainTex;float4 _MainTex_ST;sampler2D _CameraDepthTexture;fixed4 _Color;v2f vert (appdata v){v2f o;o.vertex = UnityObjectToClipPos(v.vertex);o.uv = TRANSFORM_TEX(v.uv, _MainTex);o.screenPos = ComputeScreenPos(o.vertex);return o;}float3 DepthToWorldPosition(float4 screenPos){float depth = Linear01Depth(UNITY_SAMPLE_DEPTH(tex2Dproj(_CameraDepthTexture,screenPos)));//线性深度值float4 ndcPos = (screenPos/screenPos.w) * 2 - 1;  //除以w是归一化Unity提供的屏幕坐标[0,1]  *2-1操作 转[-1,1]得到ndc(仅有x,y有效位)float3 clipPos = float3(ndcPos.x, ndcPos.y, 1) * _ProjectionParams.z;  //ndc补z位，直接用1 远平面值，之后乘以far远平面距离得到裁剪坐标//clipPos还缺一个w，实际z值就是w值故完整clipPos是(clipPos.xyzz) 再直接转视图空间得到远平面的视图空间坐标点（即Depth为1的点）                float3 viewPos = mul(unity_CameraInvProjection, clipPos.xyzz).xyz * depth; //*depth相当于一个Lerp操作，depth是[0,1]范围的值，取到depth深度的视图点float3 worldPos = mul(UNITY_MATRIX_I_V,float4(viewPos, 1)).xyz; //视图转世界坐标return worldPos;}fixed4 frag (v2f i) : SV_Target{float3 worldPos = DepthToWorldPosition(i.screenPos);float4 localPos = mul(unity_WorldToObject, float4(worldPos, 1.0));clip(float3(0.5,0.5,0.5) - abs(localPos.xyz));fixed2 decalUV = fixed2(localPos.x, localPos.z);decalUV = decalUV + 0.5; //模型空间 [-0.5,0.5] => [0,1] uv空间fixed4 color = tex2D(_MainTex, decalUV) * _Color;return color;}ENDCG}}
}

玩家胶囊体脚本：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class Player3D : MonoBehaviour
{public GameObject greenPrefab;public GameObject redPrefab;public int size = 5;public Terrain terrain;private CharacterController characterController;private float h;private float v;private float verticalVelocity;public float moveSpeed = 1;// Start is called before the first frame updatevoid Start(){Vector3 pos = transform.position;int halfSize = Mathf.FloorToInt(size / 2);for (int i = -halfSize; i <= halfSize; i++){for (int j = -halfSize; j <= halfSize; j++){int v = Mathf.Abs(i) + Mathf.Abs(j);if (v <= halfSize){GameObject go = GameObject.Instantiate(v == halfSize ? redPrefab : greenPrefab, transform);go.transform.position = new Vector3(pos.x + i, pos.y, pos.z + j);}}}characterController = GetComponent<CharacterController>();GetComponent<MeshRenderer>().material.renderQueue = 3001; //将人物放到贴花物体之后渲染，不被贴花物体影响}private void Update(){float h = Input.GetAxis("Horizontal");float v = Input.GetAxis("Vertical");Vector3 moveDir = transform.forward * v + transform.right * h;if (!characterController.isGrounded){verticalVelocity -= 9.8f * Time.deltaTime;moveDir.y = verticalVelocity;}else{verticalVelocity = -0.5f;}characterController.Move(moveDir * moveSpeed * Time.deltaTime);}
}

二、Post Process 辉光Bloom效果 + 矩形渐隐

Package Manager导入Post Processing

需确保摄像机开启HDR，查看相应的Graphics Settings设置

如果你的是安卓环境，那么就要去看安卓下的HDR是否开启，如果你是URP、HDRP，则是看对应管线资源的配置是否有开启HDR。

摄像机挂上后处理组件 Post-process Layer，并设置摄像机和Layer要勾选我们想要辉光效果的层级，例如自定义的HDR层

创建一个PostProcess空物体，添加如下图组件Post-process Volume，并且设置它的Layer为HDR

点击组件的New按钮会创建一个Profile资源，再点击Add effect... 添加Unity -> Bloom曝光效果

设置Intensity强度适当5~10左右
Threshold阈值[0,1]范围保持默认即可（如果你设置大于1会导致曝光效果几乎没有）
Soft Knee 软曝光？可以自定义
Diffusion 漫反射，当曝光的地形在有漫反射的物体上时会叠加漫反射的强度好像，反正我不需要拉到最左边即可（即1）其他请自行研究，如下图即可得到gif图效果，如果没有辉光说明Layer层级设置不对，所有需要辉光的物体都要设置Layer层级是HDR（由Post-process Layer指定的层级）

贴花Shader脚本修改如下：

Shader "Unlit/SimpleDecal"
{Properties{_MainTex ("Texture", 2D) = "white" {}[HDR]_Color ("Color", Color) = (1,1,1,1)_Range ("Range", Range(0,0.5)) = 0.45_FadeIntensity ("Fade Intensity", float) = 2}SubShader{Tags { "RenderType"="Transparent" "Queue"="Transparent" }LOD 100Pass{Blend SrcAlpha OneMinusSrcAlphaZWrite OffZTest OffCull FrontCGPROGRAM#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;float4 screenPos : TEXCOORD3;};sampler2D _MainTex;float4 _MainTex_ST;sampler2D _CameraDepthTexture;fixed4 _Color;float _Range;float _FadeIntensity;v2f vert (appdata v){v2f o;o.vertex = UnityObjectToClipPos(v.vertex);o.uv = TRANSFORM_TEX(v.uv, _MainTex);o.screenPos = ComputeScreenPos(o.vertex);return o;}float3 DepthToWorldPosition(float4 screenPos){float depth = Linear01Depth(UNITY_SAMPLE_DEPTH(tex2Dproj(_CameraDepthTexture,screenPos)));//线性深度值float4 ndcPos = (screenPos/screenPos.w) * 2 - 1;  //除以w是归一化Unity提供的屏幕坐标[0,1]  *2-1操作 转[-1,1]得到ndc(仅有x,y有效位)float3 clipPos = float3(ndcPos.x, ndcPos.y, 1) * _ProjectionParams.z;  //ndc补z位，直接用1 远平面值，之后乘以far远平面距离得到裁剪坐标//clipPos还缺一个w，实际z值就是w值故完整clipPos是(clipPos.xyzz) 再直接转视图空间得到远平面的视图空间坐标点（即Depth为1的点）                float3 viewPos = mul(unity_CameraInvProjection, clipPos.xyzz).xyz * depth; //*depth相当于一个Lerp操作，depth是[0,1]范围的值，取到depth深度的视图点float3 worldPos = mul(UNITY_MATRIX_I_V,float4(viewPos, 1)).xyz; //视图转世界坐标return worldPos;}fixed4 frag (v2f i) : SV_Target{float3 worldPos = DepthToWorldPosition(i.screenPos);float4 localPos = mul(unity_WorldToObject, float4(worldPos, 1.0));clip(float3(0.5,0.5,0.5) - abs(localPos.xyz));fixed2 decalUV = fixed2(localPos.x, localPos.z);decalUV = decalUV + 0.5; //模型空间 [-0.5,0.5] => [0,1] uv空间fixed4 color = tex2D(_MainTex, decalUV) * _Color;//由外到内渐隐 （圆形渐隐）//float2 center = float2(0.5, 0.5);//float alpha = lerp(0, distance(float2(0,0), center), distance(decalUV, center));//color.a *= alpha;//由外到内渐隐（矩形渐隐）fixed2 uv = decalUV - 0.5; //转[-0.5,0.5]空间 方便计算float x = abs(uv.x) - _Range;float y = abs(uv.y) - _Range;               //float sum = x+y ;//max(0, x) + max(0, y);float sum = max(x, y);//color.a *= smoothstep(0, (0.5 - _Range) * 2, sum);color.a *= smoothstep(0, (0.5 - _Range) * _FadeIntensity, sum);return color;}ENDCG}}
}

有些bug就是Scene场景看不到贴花地形了，暂时没研究处来是啥情况