Shader 使图片围绕自己中心旋转(主要是用于旋转的loading界面)

Shader "LoadingImage"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		
		_Speed ("Speed",float) = 2
	}
	SubShader
	{
		// No culling or depth
		//Cull Off ZWrite Off ZTest Always
         Tags
        { 
            "Queue"="Transparent" 
            //"IgnoreProjector"="True" 
            "RenderType"="Transparent" 
            //"PreviewType"="Plane"
            //"CanUseSpriteAtlas"="True"
        }

        Stencil  
        {  
            Ref[_Stencil]  
            Comp[_StencilComp]  
            Pass[_StencilOp]  
            ReadMask[_StencilReadMask]  
            WriteMask[_StencilWriteMask]  
        }  

        LOD 200
        //Cull Off
        //Lighting Off
        //ZWrite Off
        Fog { Mode Off }
        Blend SrcAlpha OneMinusSrcAlpha

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma multi_compile DUMMY PIXELSNAP_ON
			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 vertex : SV_POSITION;
			};

            float _Speed;
            
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = v.uv;
				return o;
			}
			
			sampler2D _MainTex;

			fixed4 frag (v2f i) : SV_Target
			{
			    float2 tempUV = i.uv;
			    
			    tempUV -= float2(0.5f, 0.5f);
			    
			    if (length(tempUV) > 0.5)
			    {
			        return fixed4(0, 0, 0, 0);
			    }
			    
			    float2 finalUV = 0;
			    
			    float angle = _Time.x * _Speed;
			    
			    finalUV.x = tempUV.x * cos(angle) - tempUV.y * sin(angle);
			    
			    finalUV.y = tempUV.x * sin(angle) + tempUV.y * cos(angle);
			    
			    finalUV += float2(0.5f, 0.5f);
				fixed4 col = tex2D(_MainTex, finalUV);
				// just invert the colors
				//col.rgb = 1 - col.rgb;
				
				
				return col;
			}
			ENDCG
		}
	}
}