capture.png

Converter.cs

using UnityEngine;

public class Converter
{
    public static Texture2D ConvertTextureUV(Texture tex, Mesh mesh, int width = 512, int height = 512)
    {
        var rt = new RenderTexture(width, height, 0, RenderTextureFormat.ARGB32);
        RenderTexture.active = rt;
        GL.Clear(true, true, Color.clear);

        uvConverter.mainTexture = tex;
        uvConverter.SetFloat("_Alpha", 1f);
        uvConverter.SetPass(0);
        Graphics.SetRenderTarget(rt);
        Graphics.DrawMeshNow(mesh, Matrix4x4.identity);

        var tex2d = RtToT2d(rt, RenderTextureFormat.ARGB32);
        rt.Release();
        return tex2d;
    }
    static Material uvConverter { get { if (_converter == null) _converter = new Material(Shader.Find("Unlit/CopyTextureUV0ToUV1")); return _converter; } }
    static Material _converter;

    static Texture2D RtToT2d(RenderTexture rt, TextureFormat format)
    {
        var tex2d = new Texture2D(rt.width, rt.height, format, false);
        var rect = Rect.MinMaxRect(0f, 0f, tex2d.width, tex2d.height);
        RenderTexture.active = rt;
        tex2d.ReadPixels(rect, 0, 0);
        RenderTexture.active = null;
        tex2d.Apply();
        return tex2d;
    }
}

CopyTextureUV0ToUV1.shader

Shader "Unlit/CopyTextureUV0ToUV1"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_Alpha ("alpha val", Float) = 0
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100 ZTest Always Cull Off

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

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
				float2 uv2 : TEXCOORD1;
			};

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

			sampler2D _MainTex;
			float4 _MainTex_ST;
			float _Alpha;
			
			v2f vert (appdata v)
			{
				v.uv2.y = 1.0-v.uv2.y;

				v2f o;
				o.vertex = float4(v.uv2*2.0-1.0,0.0,1.0);
				o.uv = v.uv;
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				col.a *= _Alpha;
				return col;
			}
			ENDCG
		}
	}
}

origin.png

uvConverted.png