Path Tracer -- Always get flat shading

I implemented:

• calculateBSDF
• calculateFresnel
• calculateTransmissionDirection.
• stream compaction

But the rendered picture I got is always flat shading. And the color doesn't looks right.

The problem is that in remove_if function I accidentally remove all the rays that need to continue tracing. For the colors, that is because I used plus instead of multiply.

Correctted that I got this: