Преобразование старой позиции в HClip

Pass
        {
            // Lightmode tag required setup motion vector parameters by C++ (legacy Unity)
            Tags{ "LightMode" = "MotionVectors" }
            
            HLSLPROGRAM
            // Required to compile gles 2.0 with standard srp library
            #pragma prefer_hlslcc gles
            #pragma exclude_renderers d3d11_9x
            #pragma target 3.0

            //--------------------------------------
            // GPU Instancing
            #pragma multi_compile_instancing

            #pragma vertex vert
            #pragma fragment frag

            // -------------------------------------
            // Includes

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            
            // -------------------------------------
            // Structs
            struct Attributes
            {
                float4 position             : POSITION;
                float3 positionOld          : TEXCOORD4;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct Varyings
            {
                float4 positionCS           : SV_POSITION;
                float4 previousPositionCS   : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };

            // -------------------------------------
            // Vertex
            Varyings vert(Attributes input)
            {
                Varyings output = (Varyings)0;

                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_TRANSFER_INSTANCE_ID(input, output);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);

                output.positionCS = TransformObjectToHClip(input.position.xyz);

                // this works around an issue with dynamic batching
                // potentially remove in 5.4 when we use instancing
                #if defined(UNITY_REVERSED_Z)
                    output.positionCS.z -= unity_MotionVectorsParams.z * output.positionCS.w;
                #else
                    output.positionCS.z += unity_MotionVectorsParams.z * output.positionCS.w;
                #endif                

                const float4 prevPos = (unity_MotionVectorsParams.x == 1) ? float4(input.positionOld, 1) : input.position;
                output.previousPositionCS = mul(UNITY_MATRIX_VP, mul(unity_MatrixPreviousM, prevPos));
                return output;
            }


            // -------------------------------------
            // Fragment
            float2 frag(Varyings input) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);

                //Note: unity_MotionVectorsParams.y is 0 is forceNoMotion is enabled
                bool forceNoMotion = unity_MotionVectorsParams.y == 0.0;
                if (forceNoMotion)
                {
                   return float2(0.0, 0.0);
                }

                // Calculate positions
                float2 currTCPos = input.positionCS.xy * (_ScreenSize.zw * 2);
                float2 prevTCPos = input.previousPositionCS.xy * (_ScreenSize.zw * 2);
                return currTCPos.xy;
                //return prevTCPos.xy;
            }
            ENDHLSL
        }