Clipping in Volume rendering view

I’m trying to use the example code to do volume rendering, but some how the entire volume is clipping when I’m moving the camera position as below.

The result from the example ( show entire volumes without clipping.

Does anyone know what’s happening? I thought about the near and far value of the camera, but it doesn’t give any changes. When I replace the entire volume texture with a single color, and it shows a full-size 3D box, but the result from the ray casting shows such a clipped result.