Unity 播放 带 alpha 通道的视频（Video Player组件）

webm类型文件

格式转换插件：https://www.fnordware.com/WebM/

或者用shader实现

```

Shader "SYN/BlackScreenClipTex" {

Properties{

_Color("Alpha Color Key", Color) = (0,0,0,1)

_MainTex("Albedo (RGB)", 2D) = "white" {}

_Range("Range",Range(0,1.01)) = 0.1

}

SubShader{

Tags{ "RenderType" = "Opaque" }

LOD 200

CGPROGRAM

#pragma surface surf BlinnPhong Alpha Blending

#pragma target 3.0

sampler2D _MainTex;

struct Input {

float2 uv_MainTex;

};

float _Range;

float4 _Color;

void surf(Input IN, inout SurfaceOutput o)

{

half4 cc = tex2D(_MainTex, IN.uv_MainTex);

float v = (cc.r + cc.g + cc.b) / 3;

v = 1 - v;

half4 color = half4(v, v, v, v);

float4 oo = float4(1, 0, 0, 0.2);

half4 c = color;

oo.rgb = c.rgb;

if (abs(c.r - _Color.r)<_Range && abs(c.g - _Color.g)<_Range && abs(c.b - _Color.b)<_Range)

{

clip(o.Alpha - 1);

}

else

{

o.Emission = cc;

}

}

ENDCG

}

FallBack "Diffuse"

}

```