use Equirectangular picture for unity skybox

equiSkyBoxUnity.shader

Shader "Skybox/Equirectangular" {
	Properties{
		_Tint("Tint Color", Color) = (.5, .5, .5, .5)
		[Gamma] _Exposure("Exposure", Range(0, 8)) = 1.0
		_Rotation("Rotation", Range(0, 360)) = 0
		[NoScaleOffset] _Tex("Panorama (HDR)", 2D) = "grey" {}
	}

		SubShader{
		Tags{ "Queue" = "Background" "RenderType" = "Background" "PreviewType" = "Skybox" }
		Cull Off ZWrite Off

		Pass{

		CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "UnityCG.cginc"

		sampler2D _Tex;
	half4 _Tex_HDR;
	half4 _Tint;
	half _Exposure;
	float _Rotation;

	float4 RotateAroundYInDegrees(float4 vertex, float degrees)
	{
		float alpha = degrees * UNITY_PI / 180.0;
		float sina, cosa;
		sincos(alpha, sina, cosa);
		float2x2 m = float2x2(cosa, -sina, sina, cosa);
		return float4(mul(m, vertex.xz), vertex.yw).xzyw;
	}

	struct appdata_t {
		float4 vertex : POSITION;
	};

	struct v2f {
		float4 vertex : SV_POSITION;
		float3 texcoord : TEXCOORD0;
	};

	v2f vert(appdata_t v)
	{
		v2f o;
		o.vertex = mul(UNITY_MATRIX_MVP, RotateAroundYInDegrees(v.vertex, _Rotation));
		o.texcoord = v.vertex.xyz;
		return o;
	}

	fixed4 frag(v2f i) : SV_Target
	{
		float3 dir = normalize(i.texcoord);
		float2 longlat = float2(atan2(dir.x, dir.z) + UNITY_PI, acos(-dir.y));
		float2 uv = longlat / float2(2.0 * UNITY_PI, UNITY_PI);
		half4 tex = tex2D(_Tex, uv);
		half3 c = DecodeHDR(tex, _Tex_HDR);
		c = c * _Tint.rgb * unity_ColorSpaceDouble.rgb;
		c *= _Exposure;

		return half4(c, 1);
	}
		ENDCG
	}
	}


		Fallback Off

}