Relationship of WorldPoint, ScreenPoint, and ViewportPoint

Hi guys, I have some questions to ask you.

I understand the concept of WorldPoint, ScreenPoint, and ViewportPoint (will write as WP, SP, and VP from now). Unity has great converting function as WorldToViewportPoint, WorldToScreenPoint. At this point, I became curious on the calculation of how it basically works.

For example, my Target Object is located at (-9.29, 3.11, 2.27). the Camera is located at (2.89, 0.998, -10.062).

By using conversion function above, result shows VP = (0.837, 0.568, 13.906) SP = (1269.349, 493.995, 13.90631) // Screen size is 1024*768

I found few different 4x4 Matrices (CameratoWorld, WorldtoCamera, Projection). So here's my question. By using these matrices and points, how can I calcaulte(convert) WP to VP? or is there any other factors that I would need to consider through the process? If you let me know the relationship equation, it will be perfect!

Thanks.