Unity Shader 实现刮刮乐效果
发表于2018-11-20
网上关于实现刮刮乐的文章有很多，可以使用UGUI实现刮刮乐效果，也可以使用shader来实现，本篇中给大家分享的是第二种，利用Shader实现刮刮乐效果。
实现思路：
1.当按下鼠标时，我们就克隆一个笔刷，这样就形成了涂画的效果。
2.然后我们写一个遮罩shader，shader中需要两张图，一张是遮罩的图片（，另一张是用于剔除遮罩的图片，我们将渲染出的rendertexture作为剔除遮罩的图片。这样就完成了刮刮乐效果。
实现代码
MaskShader：
Shader "Unlit/MaskShader"
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Properties
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_MainTex ("Texture", 2D) = "white" ｛｝
_MaskDecalTex("Mask Decal Texture", 2D) = "white" ｛｝
_MaskOffset("Mask Offset", vector) = (0,0,0,0)
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SubShader
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Tags ｛ "RenderType"="Opaque" ｝
LOD 100
Pass
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CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
#include "UnityCG.cginc"
struct appdata
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float4 vertex : POSITION;
float2 uv : TEXCOORD0;
｝;
struct v2f
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float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
｝;
sampler2D _MainTex;
float4 _MainTex_ST;
float4 _MaskOffset;
sampler2D _MaskDecalTex;
v2f vert (appdata v)
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v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
return o;
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fixed4 frag (v2f i) : SV_Target
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fixed4 r = tex2D(_MainTex, i.uv);
#if UNITY_UV_STARTS_AT_TOP
float grabSign = -_ProjectionParams.x;
#else
float grabSign = _ProjectionParams.x;
#endif
half2 uv = float2(1, grabSign) * (i.uv - half2(0.5, 0.5)) / _MaskOffset.ww + half2(0.5, 0.5);
fixed4 mask = tex2D(_MaskDecalTex, uv + _MaskOffset.xy);
return r + mask;
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ENDCG
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BlendShader：
Shader "Unlit/BlendShader"
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Properties
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_MainTex ("Texture", 2D) = "white" ｛｝
_SecondTex("Second Texture", 2D) = "white" ｛｝
_MaskTex("Mask Texture", 2D) = "white" ｛｝
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SubShader
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Tags ｛ "RenderType"="Opaque" ｝
LOD 100
Pass
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CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
#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;
sampler2D _SecondTex;
sampler2D _MaskTex;
v2f vert (appdata v)
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v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
return o;
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fixed4 frag (v2f i) : SV_Target
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fixed4 col1 = tex2D(_MainTex, i.uv);
fixed4 col2 = tex2D(_SecondTex, i.uv);
#if UNITY_UV_STARTS_AT_TOP
float grabSign = -_ProjectionParams.x;
#else
float grabSign = _ProjectionParams.x;
#endif
half2 uv = float2(1, grabSign) * (i.uv - half2(0.5, 0.5)) + half2(0.5, 0.5);
fixed4 mask = tex2D(_MaskTex, uv);
return lerp(col1, col2, mask.a);
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ENDCG
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脚本(核心部分)：
Vector4 viewPortPoint = Camera.main.WorldToViewportPoint(maskMappingPoint.position);
viewPortPoint -= new Vector4(0.5f, 0.5f);
viewPortPoint.w = maskMappingPoint.localScale.x;
if (mPersistMaskTex == null)
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mPersistMaskTex = new Texture2D(src.width, src.height, TextureFormat.RGBA32, false, true);
for (int x = 0; x < mPersistMaskTex.width; x++)
for (int y = 0; y < mPersistMaskTex.height; y++)
mPersistMaskTex.SetPixel(x, y, new Color(0, 0, 0, 0));
mPersistMaskTex.Apply();
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maskMat.SetTexture("_MainTex", mPersistMaskTex);
maskMat.SetVector("_MaskOffset", viewPortPoint);
Graphics.Blit(mPersistMaskTex, maskRT, maskMat);
blendMat.SetTexture("_MainTex", src);
blendMat.SetTexture("_SecondTex", tempRT);
blendMat.SetTexture("_MaskTex", maskRT);
Graphics.Blit(src, des, blendMat);
var cacheActive = RenderTexture.active;
RenderTexture.active = maskRT;
mPersistMaskTex.ReadPixels(new Rect(0, 0, mPersistMaskTex.width, mPersistMaskTex.height), 0, 0);
mPersistMaskTex.Apply();
RenderTexture.active = cacheActive;