a question about raydir in skybox shader

[VincentGogo]

float3 rayStart = _CameraPos;
float3 rayDir = normalize(mul((float3x3)unity_ObjectToWorld, i.vertex));

I think rayDir should be below code, is that right?
float3 rayDir = normalize(mul((float3x3)unity_ObjectToWorld, i.vertex) - rayStart )