VRでテクスチャをスクリーンスペースに表示するやつ

ScreenSpaceTexture.hlsl

            float _Alpha;
            sampler2D _MainTex;
            float4 _MainTex_TexelSize;
            float _Scale;

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float4 screenPos : TEXCOOR0;
                float aspect : TEXCOORD1;
            };
            
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.screenPos = ComputeScreenPos(o.vertex);
                // (tex h / tex w) * (screen w / screen h)
                o.aspect = _MainTex_TexelSize.w * _MainTex_TexelSize.x * _ScreenParams.x * (_ScreenParams.w - 1);
                return o;
            }
            
            fixed4 frag(v2f i) : SV_Target
            {
                half4 col;
                float2 uv = i.screenPos.xy / i.screenPos.w;
#if UNITY_SINGLE_PASS_STEREO
                float4 scaleOffset = unity_StereoScaleOffset[unity_StereoEyeIndex];
                uv = (uv - scaleOffset.zw) / scaleOffset.xy;
#endif
                float a = i.aspect;
                uv.x = uv.x * a - (a - 1) * 0.5;
                uv -= 0.5;
                uv *= _Scale;
                uv += 0.5;
                col.rgb = tex2D(_MainTex, uv).rgb;
                col.a = _Alpha;
                return col;
            }