Unity中对sprite renderer图片做进度条效果

项目里条件限制，只能使用sprite renderer来做UI，原来做进度条效果都是用ngui或者ugui里写好的fill属性。想到肯定可以用shader来实现，但是无奈自己并不会写 T T 。找到个能用的shader，记录下地址：

http://www.ceeger.com/forum/read.php?tid=3492;ds=1#tpc

感谢原作者。

shader的内容：

Shader "Custom/CursorLoadShader" {
Properties
{
_Color ("Main Color", Color) = (1,1,1,1)
_MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
_MaskTex ("Mask (A)", 2D) = "white" {}
_Progress ("Progress", Range(0,1)) = 0.5
}

Category
{
Lighting Off
ZWrite Off
Cull back
Fog { Mode Off }
Tags {"Queue"="Transparent" "IgnoreProjector"="True"}
Blend SrcAlpha OneMinusSrcAlpha
SubShader
{
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
sampler2D _MainTex;
sampler2D _MaskTex;
fixed4 _Color;
float _Progress;
struct appdata
{
float4 vertex : POSITION;
float4 texcoord : TEXCOORD0;
};
struct v2f
{
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
v2f vert (appdata v)
{
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
o.uv = v.texcoord.xy;
return o;
}
half4 frag(v2f i) : COLOR
{
fixed4 c = _Color * tex2D(_MainTex, i.uv);
fixed ca = tex2D(_MaskTex, i.uv).a;
c.a *= ca >= _Progress ? 0 : 1;
return c;
}
ENDCG
}
}

SubShader
{
AlphaTest LEqual [_Progress]
Pass
{
SetTexture [_MaskTex] {combine texture}
SetTexture [_MainTex] {combine texture, previous}
}
}

}
Fallback "Transparent/VertexLit"
}

圆环形遮罩图片