The third day of filming was taken down the alleyway later on in the evening again to keep the lighting similar. A 5D camera, pop up greenscreen, tripod, and fish eye lense (for taking HDRI which would be useful for 3D objects) were used:

The final process was to rotoscope the top and bottom of the door alongside the greenscreen which   was tested and usable results. The measuring of the tripod also meant matching the shots up was easier.

The next shot is of the character walking down the hallway, the green screen was placed at the end of the corridor.

 A shot was taken from low down, and created on the day of filming to help cut up the long shot of following the character down the hallway. Rotoscoping of the doorway and character were needed before implementation of the proxy 3D models.

The next shot was of the character walking forward, hearing a noise and turning around:

 A close up was then taken to show the characters fear, which has been always kept at a distance. The character looks up at the vent above, the shot then switches to a point of view from the character looking up at the cealing. The 3D grate would then fall off.

The next shot, another point of view, was to show the 3D grate hitting the floor, and the character backing off, switching to the close up again to keep continuity:

Finally the camera would pan up to show the vent, and the creatures legs coming into view as it prepares to jump:

This shot was of the ceiling with the camera backing away, as a point of view from the character, the 3D vent and headcrab would be implemented at a later date.

With the days filming finished, a last establishing shot was taken, in which the Citadel would be implemented in the back, and the shot dirtied and decayed using Photoshop:

Once the filming was complete, a rough edit was put together of all the current footage at the time, which would then be reviewed and re-edited at a later date: