How to use equirectangular image in Unity to look around in 360 mode?

First, you need a shader file. Here is a shader code you can use to make shader file called InsideVisible:

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

// Based on Unlit shader, but culls the front faces instead of the back

Shader "InsideVisible" {
Properties {
	_MainTex ("Base (RGB)", 2D) = "white" {}
}

SubShader {
	Tags { "RenderType"="Opaque" }
	Cull front    // ADDED BY BERNIE, TO FLIP THE SURFACES
	LOD 100
	
	Pass {  
		CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			
			#include "UnityCG.cginc"

			struct appdata_t {
				float4 vertex : POSITION;
				float2 texcoord : TEXCOORD0;
			};

			struct v2f {
				float4 vertex : SV_POSITION;
				half2 texcoord : TEXCOORD0;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			
			v2f vert (appdata_t v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				// ADDED BY BERNIE:
				v.texcoord.x = 1 - v.texcoord.x;				
				o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				fixed4 col = tex2D(_MainTex, i.texcoord);
				return col;
			}
		ENDCG
	}
}

}

Then make a material, use your equirectangular panorama image in it. Then drag and drop the shader file to this material.

Import a high poly sphere object (for best result) to Unity scene, apply the material to it.

That’s all, now let’s figure out how to look around inside that panorama sphere. My suggestion is to use this package: https://www.youtube.com/watch?v=0W8rDJyp5QI but don’t use movement feature.

Watch the full video here: