Raycast and box-ray intersection

Basic raycast from camera and box-ray intersection finished. At this point, I can get a 2D picture now.

• Raycast:

Use the caculation steps from Computer Graphic course.
Raycast direction test:

Here is a screen shot of one of the images I got，flat shading: 

•  Box-ray intersection

I used the slab algorithm. The link is posted on the previous blog.