best way to add CGI to film

Support Lighting and Rendering
1

Hello blender forums.

I am trying to add CGi footage of my extinct moa into a forest so it looks like its alive again. I was planning on using a green screen technique and setting the “world” to green. This gave me fairly good results but i want to look as good as it can.

Is it possible to export a movie clip with an “invisible background” similar to a picture?
Whats the best way to mix CGI and real film together?

Im gonna give camera tracking a try later on but I wanted to here your opinions on this.

2

Is it possible to export a movie clip with an “invisible background” similar to a picture?

You can render out an image with a transparent background
Blender Renderer - In the Render / Shading panel set alpha to Transparent
Cycles Renderer - Enable ‘Transparent’ in the Render / Film panel

You need to render the output with an alpha channel so in the Render / Output panel enable ‘RGBA’

You also render to a format (Render / Output settings) that can actually use this alpha channel. For a movie formt you are very limited to something like Quicktime Animation codec, otherwise render to an image sequence with a format such as .png

3

… or OpenEXR.

4

the steps are:

  1. make a plan and write down what you want to show
  2. make storyboard/previs of what you want to show
  3. shoot you footage
  4. if you can shoot HDRI of the film location
  5. prepare you CG models (modelling, textures, shaders, …)
  6. edit you movie
  7. matchmove you shots
  8. light you models in the shots
  9. render you CG
  10. compositing
  11. render final images
  12. make the final movie

the first 3 steps are very import, it will save you a lot of time later in the process!
its always recomend to render to an image sequncene rather then a movie clip. if you have to stop the rendering or it crashes you can just restart after the frame it stopped. a movie clip has to be rendered always for the whole range
image sequences can give you much more flexibilty in post/compositing: you can render many layers and passes which you cant fit into a movie clip

dont try to render everything in final quality at first, do a lower quality version first and take it into compositing. then you can see very fast if something is wrong.

green screen is not necessary for CG, because you can create an alpha mask from the renderer. you would use a green screen if you film something real and want to put things behind it.

5

thanks for all the help guys, i have found a good way!

6

Glad you got it working! You remind me of myself 13 years ago. I was just starting to teach myself Blender so I could add CGI to some of my videos in the the video class I was taking. I did a Matrix spoof and couldn’t figure out how to get the bullets into the scene so I had the bright idea of doing it as a greenscreen effect and like you said, it worked pretty well, but it’s not perfect. I used this technique in several of my early shorts too, sometimes changing the background depending on the colors of my object. I think I even used pink at one point!
Then when I realized that they don’t do this in Hollywood, I started looking for how to do the transparent background thing, (alpha channel) in Blender and when I found it, I was super excited! When I did my first composite, I was blown away by how clean it looked :slight_smile:
Sorry for the rambles, but thank you for the trip down memory lane :slight_smile: