Magic of VFX

Hello there - I know I had taken a long a break! Well I was on to the usual stuff - writing stories, helping my friends on their startup endeavors, trying to get a team of interested folks to make a movie blah blah...

Anyways, I signed up for this VFX course; I had long wanted to do a low budget sci-fi movie (I have been sitting on a short story for ages)... hoping that this course will give me some insights. Yup! am liking the course (lots of info, good interviews with movie-makers, tips etc) and also linking HitFilm3.

Here is the course details: Visual Effects for Guerrilla Filmmakers from Norwich University of the Arts - a MOOC offered by www.futurelearn.com.

Here is my first attempt at VFX :)
https://youtu.be/_8oAndSb9wY

Here are my green screen attempts. 

I shot my own background footage for the day and night exercise: 
1) https://youtu.be/w4AWKg6O5HQ (original footage for day scene) 2) https://youtu.be/HygkHETJsVY (my background for day scene) 3) https://youtu.be/b3qzv_oxYMA (original footage for night scene) 4) https://youtu.be/iU7d1OE1sVA (my background for night scene)

What do you think? Good? Bad? So so?

Also do you know of any free software which no-budget movie makers like myself could use for VFX?