I have a simple system of a laser, pinhole slit, and diffraction grating and having trouble mapping the expected diffraction pattern. I have performed this experiment in real life, and can see the spots align 16 mm apart vertically after exiting the diffraction grating. 

I have moved my system to non sequential mode and ray traced, but the detector viewer continues to show one giant spot. Can someone please help me better understand what could be the issue here? I am using scattering surfaces.