//clipPos.w = 1, viewPos.z = -1
    float2 ClipXYToViewXY(float2 clipXY)
    {
        //clipXY.xy = mad(1, UNITY_MATRIX_P._m02_m12, clipXY.xy);
        clipXY.xy += UNITY_MATRIX_P._m02_m12;
        return float2(clipXY.x / UNITY_MATRIX_P._m00, clipXY.y / UNITY_MATRIX_P._m11);
    }       
           float2 InverseTransformStereoScreenSpaceTex(float2 uv, float w)
    {
        #if UNITY_SINGLE_PASS_STEREO
            
            float4 scaleOffset = unity_StereoScaleOffset[unity_StereoEyeIndex];
            uv.xy = mad(scaleOffset.zw, -w, uv.xy);
            return uv.xy / scaleOffset.xy;
        #else
            return uv;
        #endif
    }
    float2 InverseTransformStereoScreenSpaceTex(float2 uv)
    {
        #if UNITY_SINGLE_PASS_STEREO
            return InverseTransformStereoScreenSpaceTex(saturate(uv), 1);
        #else
            return uv;
        #endif
    }
       float PreComputeLinearEyeDepthFactor(in float3 viewPos){
            return mad(
            //mad(viewPos.x , UNITY_MATRIX_P._m20 , viewPos.y * UNITY_MATRIX_P._m21),
            viewPos.x * UNITY_MATRIX_P._m20 + viewPos.y * UNITY_MATRIX_P._m21 ,
            //dot(viewPos.xy,UNITY_MATRIX_P._m20_m21), 
            rcp(viewPos.z) , 
            UNITY_MATRIX_P._m22
            );
        }
          //W = 1
    float2 GrabUVToClipXY(float2 grabUV)
    {
        float2 o;
        o.xy = InverseTransformStereoScreenSpaceTex(grabUV);
        
        #if UNITY_UV_STARTS_AT_TOP
            o.x = mad(o.x, 2, -1);
            o.y = mad(o.y, -2, 1);
        #else
            o.xy = mad(o.xy, 2, -1);
            
        #endif
        return o;
    }
       ///W = 1
    float2 ScreenUVToClipXY(float2 screenUV)
    {
        float2 o;
        o.xy = InverseTransformStereoScreenSpaceTex(screenUV);
        
        
        o.xy = mad(o.xy, 2, -1);
        o.y *= _ProjectionParams.x;
        return o;
    }
    
        float LinearEyeDepth(in float zBuffer,in float linearEyeDepthFactor){
            return UNITY_MATRIX_P._m23 /(linearEyeDepthFactor + zBuffer);
        }

        float LinearEyeDepth(in float zBuffer,in float3 viewPos)
        {
            return LinearEyeDepth(zBuffer,PreComputeLinearEyeDepthFactor(viewPos));
            
        }
        //viewXY = viewPos.xy/ -viewPos.z
        float PreComputeLinearEyeDepthFactorViewXY(float2 viewXY){
            //return dot(viewXY,-UNITY_MATRIX_P._m20_m21) + UNITY_MATRIX_P._m22;
            return mad(viewXY.x , -UNITY_MATRIX_P._m20, mad(viewXY.y , -UNITY_MATRIX_P._m21 , UNITY_MATRIX_P._m22));
            //return (viewXY.x * -UNITY_MATRIX_P._m20+viewXY.y * -UNITY_MATRIX_P._m21) + UNITY_MATRIX_P._m22;
        }
        
        //viewXY = viewPos.xy/ -viewPos.z
        float LinearEyeDepthViewXY(float zBuffer, float2 viewXY)
        {
            return LinearEyeDepth(zBuffer,PreComputeLinearEyeDepthFactorViewXY(viewXY));
        }
        
        float LinearEyeDepthScreenUV(float zBuffer, float2 screenUV)
        {
            float2 viewXY = ClipXYToViewXY(ScreenUVToClipXY(screenUV));
            return LinearEyeDepthViewXY(zBuffer, viewXY);
        }
        
        float LinearEyeDepthGrabUV(float zBuffer, float2 grabUV)
        {
            
            
            float2 viewXY = ClipXYToViewXY(GrabUVToClipXY(grabUV));
            return LinearEyeDepthViewXY(zBuffer, viewXY);
            //return LinearEyeDepth(zBuffer,ClipXYWToViewPos( GrabUVToClipXYW(grabUV,1)));
        }