Why convert verRay multiply -1 not float3(1,1,-1)

[lovepurple]

hi. I have a doubt. The coordinate system of the viewing ray in the vertex is the right-handed coordinate system. It needs to be converted to the left-handed coordinate system. Why is the viewRay*=-1 operation? Instead of viewRay*=float3(-1,-1,1) or viewRay*=float3(1,1,-1)?