Screen Space warping

I’m working on a shader that allows me to use either Box blur or Gaussian blur on the Universal Render Pipeline. I have gotten everything down, but there is a problem that I can’t seem to solve. The texture seems to distort when the camera moves. I use _CameraOpaqueTexure to get the view of scene. Is there any way to solve this? I left the code here.alt text

You perform the perspective division in the vertex shader, which forces the non-linear coordinates to interpolate linearly over the surface of the object, hence the distortion;

float4 screenPos = ComputeScreenPos(vertexInput.positionCS);
o.screenPos = screenPos.xy / screenPos.w;

Move the second line into the fragment shader and it should be fine.