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【URP】Unity3D物体遮罩的多种方案实现

news 2025/10/11 20:00:58

【从UnityURP开始探索游戏渲染】专栏-直达

物体自身遮罩控制方案

基于Unity URP实现3D物体方向性动态遮罩

‌Shader核心功能‌：

通过_MaskDirection向量定义遮罩方向
使用_MaskProgress参数(0-1范围)控制显示比例
基于顶点世界坐标在遮罩方向上的投影值进行裁剪(clip)
兼容URP渲染管线标准结构

‌控制器特点‌：

支持运行时动态调整遮罩方向和进度
内置演示动画(旋转方向和进度波动)
提供外部调用接口用于程序控制
自动规范化方向向量确保计算准确

DirectionalMask.shader

Shader "Custom/DirectionalMask"
{Properties{_MainTex("Texture", 2D) = "white" {}_MaskDirection("Mask Direction", Vector) = (1,0,0,0)_MaskProgress("Mask Progress", Range(0, 1)) = 0.5}SubShader{Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" }HLSLINCLUDE#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"struct Attributes{float4 positionOS : POSITION;float2 uv : TEXCOORD0;};struct Varyings{float4 positionCS : SV_POSITION;float2 uv : TEXCOORD0;float3 positionWS : TEXCOORD1;};TEXTURE2D(_MainTex);SAMPLER(sampler_MainTex);float4 _MainTex_ST;float3 _MaskDirection;float _MaskProgress;Varyings Vert(Attributes input){Varyings output;output.positionCS = TransformObjectToHClip(input.positionOS.xyz);output.uv = TRANSFORM_TEX(input.uv, _MainTex);output.positionWS = TransformObjectToWorld(input.positionOS.xyz);return output;}half4 Frag(Varyings input) : SV_Target{half4 col = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv);// 计算物体顶点在遮罩方向上的投影比例float dotProduct = dot(normalize(input.positionWS), normalize(_MaskDirection));float normalizedDot = (dotProduct + 1) * 0.5; // 映射到0-1范围// 根据进度参数裁剪clip(normalizedDot - _MaskProgress);return col;}ENDHLSLPass{HLSLPROGRAM#pragma vertex Vert#pragma fragment FragENDHLSL}}
}

DirectionalMaskController.cs

using UnityEngine;public class DirectionalMaskController : MonoBehaviour
{[SerializeField] private Renderer _targetRenderer;[SerializeField] private Vector3 _maskDirection = Vector3.right;[Range(0, 1)] public float maskProgress = 0.5f;[SerializeField] private float _rotationSpeed = 30f;[SerializeField] private float _progressSpeed = 0.2f;private Material _material;private static readonly int MaskDirection = Shader.PropertyToID("_MaskDirection");private static readonly int MaskProgress = Shader.PropertyToID("_MaskProgress");void Start(){_material = _targetRenderer.material;UpdateShaderParams();}void Update(){// 动态旋转遮罩方向_maskDirection = Quaternion.Euler(0, _rotationSpeed * Time.deltaTime, 0) * _maskDirection;// 动态调整遮罩进度maskProgress = Mathf.PingPong(Time.time * _progressSpeed, 1f);UpdateShaderParams();}private void UpdateShaderParams(){_material.SetVector(MaskDirection, _maskDirection.normalized);_material.SetFloat(MaskProgress, maskProgress);}// 外部调用接口public void SetMaskDirection(Vector3 newDirection){_maskDirection = newDirection.normalized;UpdateShaderParams();}public void SetMaskProgress(float progress){maskProgress = Mathf.Clamp01(progress);UpdateShaderParams();}
}

‌扩展：

可添加_MaskSharpness参数控制边缘过渡柔和度
结合Stencil Buffer实现多物体遮罩叠加
通过AnimationCurve控制进度变化曲线

该方案相比基础遮罩实现增加了方向向量参数和动态进度控制，通过顶点投影计算实现方向性裁剪效果。控制器脚本支持运行时动态调整所有参数，并保持与Shader的高效数据交互。

‌HLSL Shader实现‌（基于透明度遮罩）：

unity_urp遮罩shader

Shader "Custom/TransparentColorURP" {Properties {_Color("Color Tint", Color) = (1,1,1,1)_MainTex("Main Tex", 2D) = "white" {}_AlphaScale("Alpha Scale", Range(0, 1)) = 0.5}SubShader {Pass {ZWrite OnColorMask 0}Pass {ZWrite OffBlend SrcAlpha OneMinusSrcAlpha// HLSL代码...}}
}

‌控制脚本‌：

unity_遮罩控制脚本

public class MaskController : MonoBehaviour {public Renderer targetRenderer;public float maskProgress = 0.5f;void Update() {targetRenderer.material.SetFloat("_AlphaScale", Mathf.PingPong(Time.time, 1f));}
}

模板测试实现方案

‌模板Shader核心代码‌：

创建一个四边形，将StencilMask做成材质赋给它。通过调整四边形的大小，来调整遮罩区域。
当然也可在c#端动态调整mesh的点来做动态异形遮罩。
将需要被遮罩的URP中Lit的物体，换成StencilLit的shader。这样原来的Lit的物体就支持StencilMask的遮罩了。

StencilMask.shader

Shader "Custom/StencilMask"
{SubShader{Tags { "RenderType"="Opaque" "Queue"="Geometry-100" }Pass{ColorMask 0ZWrite OffStencil {Ref 1Comp AlwaysPass Replace}}}
}

StencilLit.shader

Shader "Universal Render Pipeline/StencilLit"
{Properties{// Specular vs Metallic workflow_WorkflowMode("WorkflowMode", Float) = 1.0[MainTexture] _BaseMap("Albedo", 2D) = "white" {}[MainColor] _BaseColor("Color", Color) = (1,1,1,1)_Cutoff("Alpha Cutoff", Range(0.0, 1.0)) = 0.5_Smoothness("Smoothness", Range(0.0, 1.0)) = 0.5_SmoothnessTextureChannel("Smoothness texture channel", Float) = 0_Metallic("Metallic", Range(0.0, 1.0)) = 0.0_MetallicGlossMap("Metallic", 2D) = "white" {}_SpecColor("Specular", Color) = (0.2, 0.2, 0.2)_SpecGlossMap("Specular", 2D) = "white" {}[ToggleOff] _SpecularHighlights("Specular Highlights", Float) = 1.0[ToggleOff] _EnvironmentReflections("Environment Reflections", Float) = 1.0_BumpScale("Scale", Float) = 1.0_BumpMap("Normal Map", 2D) = "bump" {}_Parallax("Scale", Range(0.005, 0.08)) = 0.005_ParallaxMap("Height Map", 2D) = "black" {}_OcclusionStrength("Strength", Range(0.0, 1.0)) = 1.0_OcclusionMap("Occlusion", 2D) = "white" {}[HDR] _EmissionColor("Color", Color) = (0,0,0)_EmissionMap("Emission", 2D) = "white" {}_DetailMask("Detail Mask", 2D) = "white" {}_DetailAlbedoMapScale("Scale", Range(0.0, 2.0)) = 1.0_DetailAlbedoMap("Detail Albedo x2", 2D) = "linearGrey" {}_DetailNormalMapScale("Scale", Range(0.0, 2.0)) = 1.0[Normal] _DetailNormalMap("Normal Map", 2D) = "bump" {}// SRP batching compatibility for Clear Coat (Not used in Lit)[HideInInspector] _ClearCoatMask("_ClearCoatMask", Float) = 0.0[HideInInspector] _ClearCoatSmoothness("_ClearCoatSmoothness", Float) = 0.0// Blending state_Surface("__surface", Float) = 0.0_Blend("__blend", Float) = 0.0_Cull("__cull", Float) = 2.0[ToggleUI] _AlphaClip("__clip", Float) = 0.0[HideInInspector] _SrcBlend("__src", Float) = 1.0[HideInInspector] _DstBlend("__dst", Float) = 0.0[HideInInspector] _SrcBlendAlpha("__srcA", Float) = 1.0[HideInInspector] _DstBlendAlpha("__dstA", Float) = 0.0[HideInInspector] _ZWrite("__zw", Float) = 1.0[HideInInspector] _BlendModePreserveSpecular("_BlendModePreserveSpecular", Float) = 1.0[HideInInspector] _AlphaToMask("__alphaToMask", Float) = 0.0[ToggleUI] _ReceiveShadows("Receive Shadows", Float) = 1.0// Editmode props_QueueOffset("Queue offset", Float) = 0.0// ObsoleteProperties[HideInInspector] _MainTex("BaseMap", 2D) = "white" {}[HideInInspector] _Color("Base Color", Color) = (1, 1, 1, 1)[HideInInspector] _GlossMapScale("Smoothness", Float) = 0.0[HideInInspector] _Glossiness("Smoothness", Float) = 0.0[HideInInspector] _GlossyReflections("EnvironmentReflections", Float) = 0.0[HideInInspector][NoScaleOffset]unity_Lightmaps("unity_Lightmaps", 2DArray) = "" {}[HideInInspector][NoScaleOffset]unity_LightmapsInd("unity_LightmapsInd", 2DArray) = "" {}[HideInInspector][NoScaleOffset]unity_ShadowMasks("unity_ShadowMasks", 2DArray) = "" {}}SubShader{// Universal Pipeline tag is required. If Universal render pipeline is not set in the graphics settings// this Subshader will fail. One can add a subshader below or fallback to Standard built-in to make this// material work with both Universal Render Pipeline and Builtin Unity PipelineTags{"RenderType" = "Opaque""RenderPipeline" = "UniversalPipeline""UniversalMaterialType" = "Lit""IgnoreProjector" = "True"}LOD 300// ------------------------------------------------------------------//  Forward pass. Shades all light in a single pass. GI + emission + FogPass{// Lightmode matches the ShaderPassName set in UniversalRenderPipeline.cs. SRPDefaultUnlit and passes with// no LightMode tag are also rendered by Universal Render PipelineName "ForwardLit"Tags{"LightMode" = "UniversalForward"}// -------------------------------------// Render State CommandsBlend[_SrcBlend][_DstBlend], [_SrcBlendAlpha][_DstBlendAlpha]ZWrite[_ZWrite]Cull[_Cull]AlphaToMask[_AlphaToMask]Stencil {Ref 1Comp EqualPass Keep}HLSLPROGRAM#pragma target 2.0// -------------------------------------// Shader Stages#pragma vertex LitPassVertex#pragma fragment LitPassFragment// -------------------------------------// Material Keywords#pragma shader_feature_local _NORMALMAP#pragma shader_feature_local _PARALLAXMAP#pragma shader_feature_local _RECEIVE_SHADOWS_OFF#pragma shader_feature_local _ _DETAIL_MULX2 _DETAIL_SCALED#pragma shader_feature_local_fragment _SURFACE_TYPE_TRANSPARENT#pragma shader_feature_local_fragment _ALPHATEST_ON#pragma shader_feature_local_fragment _ _ALPHAPREMULTIPLY_ON _ALPHAMODULATE_ON#pragma shader_feature_local_fragment _EMISSION#pragma shader_feature_local_fragment _METALLICSPECGLOSSMAP#pragma shader_feature_local_fragment _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A#pragma shader_feature_local_fragment _OCCLUSIONMAP#pragma shader_feature_local_fragment _SPECULARHIGHLIGHTS_OFF#pragma shader_feature_local_fragment _ENVIRONMENTREFLECTIONS_OFF#pragma shader_feature_local_fragment _SPECULAR_SETUP// -------------------------------------// Universal Pipeline keywords#pragma multi_compile _ _MAIN_LIGHT_SHADOWS _MAIN_LIGHT_SHADOWS_CASCADE _MAIN_LIGHT_SHADOWS_SCREEN#pragma multi_compile _ _ADDITIONAL_LIGHTS_VERTEX _ADDITIONAL_LIGHTS#pragma multi_compile _ EVALUATE_SH_MIXED EVALUATE_SH_VERTEX#pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS#pragma multi_compile_fragment _ _REFLECTION_PROBE_BLENDING#pragma multi_compile_fragment _ _REFLECTION_PROBE_BOX_PROJECTION#pragma multi_compile_fragment _ _SHADOWS_SOFT _SHADOWS_SOFT_LOW _SHADOWS_SOFT_MEDIUM _SHADOWS_SOFT_HIGH#pragma multi_compile_fragment _ _SCREEN_SPACE_OCCLUSION#pragma multi_compile_fragment _ _DBUFFER_MRT1 _DBUFFER_MRT2 _DBUFFER_MRT3#pragma multi_compile_fragment _ _LIGHT_COOKIES#pragma multi_compile _ _LIGHT_LAYERS#pragma multi_compile _ _FORWARD_PLUS#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/RenderingLayers.hlsl"// -------------------------------------// Unity defined keywords#pragma multi_compile _ LIGHTMAP_SHADOW_MIXING#pragma multi_compile _ SHADOWS_SHADOWMASK#pragma multi_compile _ DIRLIGHTMAP_COMBINED#pragma multi_compile _ LIGHTMAP_ON#pragma multi_compile _ DYNAMICLIGHTMAP_ON#pragma multi_compile_fragment _ LOD_FADE_CROSSFADE#pragma multi_compile_fog#pragma multi_compile_fragment _ DEBUG_DISPLAY//--------------------------------------// GPU Instancing#pragma multi_compile_instancing#pragma instancing_options renderinglayer#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/LitForwardPass.hlsl"ENDHLSL}Pass{Name "ShadowCaster"Tags{"LightMode" = "ShadowCaster"}// -------------------------------------// Render State CommandsZWrite OnZTest LEqualColorMask 0Cull[_Cull]HLSLPROGRAM#pragma target 2.0// -------------------------------------// Shader Stages#pragma vertex ShadowPassVertex#pragma fragment ShadowPassFragment// -------------------------------------// Material Keywords#pragma shader_feature_local_fragment _ALPHATEST_ON#pragma shader_feature_local_fragment _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A//--------------------------------------// GPU Instancing#pragma multi_compile_instancing#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"// -------------------------------------// Universal Pipeline keywords// -------------------------------------// Unity defined keywords#pragma multi_compile_fragment _ LOD_FADE_CROSSFADE// This is used during shadow map generation to differentiate between directional and punctual light shadows, as they use different formulas to apply Normal Bias#pragma multi_compile_vertex _ _CASTING_PUNCTUAL_LIGHT_SHADOW// -------------------------------------// Includes#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/ShadowCasterPass.hlsl"ENDHLSL}Pass{// Lightmode matches the ShaderPassName set in UniversalRenderPipeline.cs. SRPDefaultUnlit and passes with// no LightMode tag are also rendered by Universal Render PipelineName "GBuffer"Tags{"LightMode" = "UniversalGBuffer"}// -------------------------------------// Render State CommandsZWrite[_ZWrite]ZTest LEqualCull[_Cull]HLSLPROGRAM#pragma target 4.5// Deferred Rendering Path does not support the OpenGL-based graphics API:// Desktop OpenGL, OpenGL ES 3.0, WebGL 2.0.#pragma exclude_renderers gles3 glcore// -------------------------------------// Shader Stages#pragma vertex LitGBufferPassVertex#pragma fragment LitGBufferPassFragment// -------------------------------------// Material Keywords#pragma shader_feature_local _NORMALMAP#pragma shader_feature_local_fragment _ALPHATEST_ON//#pragma shader_feature_local_fragment _ALPHAPREMULTIPLY_ON#pragma shader_feature_local_fragment _EMISSION#pragma shader_feature_local_fragment _METALLICSPECGLOSSMAP#pragma shader_feature_local_fragment _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A#pragma shader_feature_local_fragment _OCCLUSIONMAP#pragma shader_feature_local _PARALLAXMAP#pragma shader_feature_local _ _DETAIL_MULX2 _DETAIL_SCALED#pragma shader_feature_local_fragment _SPECULARHIGHLIGHTS_OFF#pragma shader_feature_local_fragment _ENVIRONMENTREFLECTIONS_OFF#pragma shader_feature_local_fragment _SPECULAR_SETUP#pragma shader_feature_local _RECEIVE_SHADOWS_OFF// -------------------------------------// Universal Pipeline keywords#pragma multi_compile _ _MAIN_LIGHT_SHADOWS _MAIN_LIGHT_SHADOWS_CASCADE _MAIN_LIGHT_SHADOWS_SCREEN//#pragma multi_compile _ _ADDITIONAL_LIGHTS_VERTEX _ADDITIONAL_LIGHTS//#pragma multi_compile _ _ADDITIONAL_LIGHT_SHADOWS#pragma multi_compile_fragment _ _REFLECTION_PROBE_BLENDING#pragma multi_compile_fragment _ _REFLECTION_PROBE_BOX_PROJECTION#pragma multi_compile_fragment _ _SHADOWS_SOFT _SHADOWS_SOFT_LOW _SHADOWS_SOFT_MEDIUM _SHADOWS_SOFT_HIGH#pragma multi_compile_fragment _ _DBUFFER_MRT1 _DBUFFER_MRT2 _DBUFFER_MRT3#pragma multi_compile_fragment _ _RENDER_PASS_ENABLED#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/RenderingLayers.hlsl"// -------------------------------------// Unity defined keywords#pragma multi_compile _ LIGHTMAP_SHADOW_MIXING#pragma multi_compile _ SHADOWS_SHADOWMASK#pragma multi_compile _ DIRLIGHTMAP_COMBINED#pragma multi_compile _ LIGHTMAP_ON#pragma multi_compile _ DYNAMICLIGHTMAP_ON#pragma multi_compile_fragment _ LOD_FADE_CROSSFADE#pragma multi_compile_fragment _ _GBUFFER_NORMALS_OCT//--------------------------------------// GPU Instancing#pragma multi_compile_instancing#pragma instancing_options renderinglayer#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"// -------------------------------------// Includes#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/LitGBufferPass.hlsl"ENDHLSL}Pass{Name "DepthOnly"Tags{"LightMode" = "DepthOnly"}// -------------------------------------// Render State CommandsZWrite OnColorMask RCull[_Cull]HLSLPROGRAM#pragma target 2.0// -------------------------------------// Shader Stages#pragma vertex DepthOnlyVertex#pragma fragment DepthOnlyFragment// -------------------------------------// Material Keywords#pragma shader_feature_local_fragment _ALPHATEST_ON#pragma shader_feature_local_fragment _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A// -------------------------------------// Unity defined keywords#pragma multi_compile_fragment _ LOD_FADE_CROSSFADE//--------------------------------------// GPU Instancing#pragma multi_compile_instancing#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"// -------------------------------------// Includes#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/DepthOnlyPass.hlsl"ENDHLSL}// This pass is used when drawing to a _CameraNormalsTexture texturePass{Name "DepthNormals"Tags{"LightMode" = "DepthNormals"}// -------------------------------------// Render State CommandsZWrite OnCull[_Cull]HLSLPROGRAM#pragma target 2.0// -------------------------------------// Shader Stages#pragma vertex DepthNormalsVertex#pragma fragment DepthNormalsFragment// -------------------------------------// Material Keywords#pragma shader_feature_local _NORMALMAP#pragma shader_feature_local _PARALLAXMAP#pragma shader_feature_local _ _DETAIL_MULX2 _DETAIL_SCALED#pragma shader_feature_local_fragment _ALPHATEST_ON#pragma shader_feature_local_fragment _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A// -------------------------------------// Unity defined keywords#pragma multi_compile_fragment _ LOD_FADE_CROSSFADE// -------------------------------------// Universal Pipeline keywords#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/RenderingLayers.hlsl"//--------------------------------------// GPU Instancing#pragma multi_compile_instancing#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"// -------------------------------------// Includes#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/LitDepthNormalsPass.hlsl"ENDHLSL}// This pass it not used during regular rendering, only for lightmap baking.Pass{Name "Meta"Tags{"LightMode" = "Meta"}// -------------------------------------// Render State CommandsCull OffHLSLPROGRAM#pragma target 2.0// -------------------------------------// Shader Stages#pragma vertex UniversalVertexMeta#pragma fragment UniversalFragmentMetaLit// -------------------------------------// Material Keywords#pragma shader_feature_local_fragment _SPECULAR_SETUP#pragma shader_feature_local_fragment _EMISSION#pragma shader_feature_local_fragment _METALLICSPECGLOSSMAP#pragma shader_feature_local_fragment _ALPHATEST_ON#pragma shader_feature_local_fragment _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A#pragma shader_feature_local _ _DETAIL_MULX2 _DETAIL_SCALED#pragma shader_feature_local_fragment _SPECGLOSSMAP#pragma shader_feature EDITOR_VISUALIZATION// -------------------------------------// Includes#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/LitMetaPass.hlsl"ENDHLSL}Pass{Name "Universal2D"Tags{"LightMode" = "Universal2D"}// -------------------------------------// Render State CommandsBlend[_SrcBlend][_DstBlend]ZWrite[_ZWrite]Cull[_Cull]HLSLPROGRAM#pragma target 2.0// -------------------------------------// Shader Stages#pragma vertex vert#pragma fragment frag// -------------------------------------// Material Keywords#pragma shader_feature_local_fragment _ALPHATEST_ON#pragma shader_feature_local_fragment _ALPHAPREMULTIPLY_ON#include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"// -------------------------------------// Includes#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"#include "Packages/com.unity.render-pipelines.universal/Shaders/Utils/Universal2D.hlsl"ENDHLSL}}FallBack "Hidden/Universal Render Pipeline/FallbackError"CustomEditor "UnityEditor.Rendering.Universal.ShaderGUI.LitShader"
}

‌RenderFeature配置要点‌：

需创建URP Renderer Feature
设置Layer Mask匹配目标层级
在后处理前添加Pass

三、其他实现方式

‌多Pass深度测试法‌：

Pass {ZTest GreaterZWrite OnColorMask 0
}
Pass {ZTest LEqual// 正常渲染...
}

‌UGUI Mask混合方案‌：

使用RectTransform确定遮罩区域
通过第二摄像机渲染3D物体
结合UI Mask组件控制显示范围

‌RenderTexture遮罩‌：

创建临时RenderTexture
使用特定Shader渲染遮罩通道
通过后期处理合成最终效果

四、方案对比

方案类型	优点	适用场景
模板测试	高性能，精确控制	角色轮廓/固定形状遮罩
多Pass	无需额外纹理	简单遮挡提示
UGUI混合	可结合UI系统	HUD元素遮罩
RenderTexture	效果最灵活	复杂动态遮罩