Mask裁切UI粒子特效或者3D模型
发表于2017-08-09
刚好前几天有人问我Mask裁切UI粒子特效或者3D模型这个问题，再加上新项目也可能用，所以这两天就研究了一下。其实如果粒子特效 和3D模型 都用RenderTexture来做的话就不会有裁切的问题，但是粒子特效用RenderTexture来做会有显示的问题，所以还是得用摄像机。废话不多说了，进入正题。
原理就是把Mask的裁切区域传给粒子特效Shader，当超出这个区域那么直接让它完全透明即可。粒子特效的源生shader大家可以去unity官网下载，我在这里把需要修改的地方标注给大家。
//add 注释中的内容就是我做修改的地方。
Shader "Particles/Additive" ｛
Properties ｛
_TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
_MainTex ("Particle Texture", 2D) = "white" ｛｝
_InvFade ("Soft Particles Factor", Range(0.01,3.0)) = 1.0
//-------------------add----------------------
_MinX ("Min X", Float) = -10
_MaxX ("Max X", Float) = 10
_MinY ("Min Y", Float) = -10
_MaxY ("Max Y", Float) = 10
//-------------------add----------------------
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Category ｛
Tags ｛ "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" ｝
Blend SrcAlpha One
AlphaTest Greater .01
ColorMask RGB
Cull Off Lighting Off ZWrite Off Fog ｛ Color (0,0,0,0) ｝
SubShader ｛
Pass ｛
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_particles
#include "UnityCG.cginc"
sampler2D _MainTex;
fixed4 _TintColor;
//-------------------add----------------------
float _MinX;
float _MaxX;
float _MinY;
float _MaxY;
//-------------------add----------------------
struct appdata_t ｛
float4 vertex : POSITION;
fixed4 color : COLOR;
float2 texcoord : TEXCOORD0;
｝;
struct v2f ｛
float4 vertex : SV_POSITION;
fixed4 color : COLOR;
float2 texcoord : TEXCOORD0;
#ifdef SOFTPARTICLES_ON
float4 projPos : TEXCOORD1;
#endif
//-------------------add----------------------
float3 vpos : TEXCOORD2;
//-------------------add----------------------
｝;
float4 _MainTex_ST;
v2f vert (appdata_t v)
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v2f o;
//-------------------add----------------------
o.vpos = v.vertex.xyz;
//-------------------add----------------------
o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
#ifdef SOFTPARTICLES_ON
o.projPos = ComputeScreenPos (o.vertex);
COMPUTE_EYEDEPTH(o.projPos.z);
#endif
o.color = v.color;
o.texcoord = TRANSFORM_TEX(v.texcoord,_MainTex);
return o;
｝
sampler2D_float _CameraDepthTexture;
float _InvFade;
fixed4 frag (v2f i) : SV_Target
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#ifdef SOFTPARTICLES_ON
floatsceneZ = LinearEyeDepth (SAMPLE_DEPTH_TEXTURE_PROJ(_CameraDepthTexture, UNITY_PROJ_COORD(i.projPos)));
float partZ = i.projPos.z;
float fade = saturate (_InvFade * (sceneZ-partZ));
i.color.a *= fade;
#endif
//-------------------add----------------------
fixed4 c =2.0f * i.color * _TintColor * tex2D(_MainTex, i.texcoord);
c.a *= (i.vpos.x >= _MinX );
c.a *= (i.vpos.x <= _MaxX);
c.a *= (i.vpos.y >= _MinY);
c.a *= (i.vpos.y <= _MaxY);
c.rgb *= c.a;
return c;
//-------------------add----------------------
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ENDCG
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然后是自己写了个类继承Mask。把Mask的区域传给shader。
using UnityEngine;
using System.Collections;
using UnityEngine.UI;
public class MyMask :Mask
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protected override void Start ()
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base.Start ();
int width = Screen.width;
int height = Screen.height;
int designWidth = 960;//开发时分辨率宽
int designHeight = 640;//开发时分辨率高
float s1 = (float)designWidth / (float)designHeight;
float s2 = (float)width / (float)height;
//目标分辨率小于 960X640的 需要计算缩放比例
float contentScale =1f;
if(s1 > s2) ｛
contentScale = s1/s2;
｝
Canvas canvas = GameObject.Find("Canvas").GetComponent
Vector2 pos;
if(RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas.transform asRectTransform, transform.position, canvas.camera, out pos))｛
ParticleSystem [] particlesSystems = transform.GetComponentsInChildren();
RectTransform rectTransform = transform as RectTransform;
float minX,minY,maxX,maxY;
minX = rectTransform.rect.x pos.x;
minY = rectTransform.rect.y pos.y;
maxX = minX rectTransform.rect.width ;
maxY = minY rectTransform.rect.height;
//这里 100 是因为ugui默认的缩放比例是100 你也可以去改这个值，但是我觉得最好别改。
foreach(ParticleSystem particleSystem in particlesSystems)
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particleSystem.renderer.sharedMaterial.SetFloat("_MinX",minX/100/contentScale);
particleSystem.renderer.sharedMaterial.SetFloat("_MinY",minY/100/contentScale);
particleSystem.renderer.sharedMaterial.SetFloat("_MaxX",maxX/100/contentScale);
particleSystem.renderer.sharedMaterial.SetFloat("_MaxY",maxY/100/contentScale);
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OK，把粒子特效直接挂在Mask下面， 就可以进行裁切了。