Optix 3.6.2 tmax error

Hi,
I am using Optix 3.6.2 with CUDA 6.0. In my ray-tracing application I tried different values of tmax, but the closest hit turns out to be the same every time. Is there something I might be missing.

Thanks

Your closest hit will always have a value of t less than tmax, where t is the distance between the ray origin and the object as a multiple of the ray’s direction vector length. If you set tmax small enough that there is no object with t between tmin and tmax, then the miss program should be called.

I forgot to mention, I was using Optix Prime and I am seeing the same hit regardless of what tmax value I put.