Making shadows for green screen

[Frank Stevn]

Try ‘track motion’ and ‘2D Shadow’.

This way you can customize and animate the character shadow.

[John Rofrano]

[john murphy] “I’ve experimented with creating a duplicate track, flipping it upside down, then fading it. It kind of looks okay, but I have to do some ugly things with the vegas track to twist it along an x, y, or z space. It’s difficult and isn’t convincing, and is murder if the character walks around.”

You are on the correct path with this technique. Here is how I would approach it:

1. Duplicate the chroma key track. This duplicate should be below the original which is good because we want the shadow to be behind the foregound.
2. (Optional) Mute the original track so we can more easily see the shadow while creating it
3. Label this new track “Shadow Mask”
4. Go into the Chromakey FX on this duplicate track/event and enable Show mask only. This will serve as a white mask.
5. Add a new track below this one and label it “Shadow”
6. Place a Generated Media Color Gradient on it and make it the same length as the chroma key event. This will be our shadow.
7. Select the preset Linear White to Black in the Color Gradient as a starting point.
8. Change the (1) point from White to Transparent
9. Move the (2) point to the bottom so that you have a black bottom fading up to a transparent top.
10. Make the “Shadow” track a Compositing Child of the “Shadow Mask” track
11. Change the Compositing Mode of the “Shadow Mask” track to Multiple (Mask)
12. Add a Gaussian Blur to the “Shadow Mask” track and you should have a pretty convincing shadow
13. Open the Parent Motion on the “Shadow Mask” track and change it to 3D Source Alpha
14. Unmute the original video track so that you can position the shadow properly
15. Adjust the parent motion so that the shadow falls in the correct direction and orientation

(note: you might want to disable “Edit in Object Space” and place the pivot point at the bottom of the screen to rotate the shadow more realistically)

Your timeline show look something like this:

You can adjust the gradient and blur to make more or less shadow.

Here is an example shadow using this technique:

As you have seen, the key to convincing green screen is the proper lighting. You must match the light sources in your green screen footage to those in the background video. If each scene has a different source of light, then you need to shoot each green screen scene with different lighting too. Not only the direction needs to match but the color temperature (indoor vs outdoor).

~jr

http://www.johnrofrano.com
http://www.vasst.com

[John Murphy]

Actually, your multi-step technique worked pretty well. I haven’t testest for my character walking yet, but basic arm movements, it follows just like a shadow would. Pretty convincing!

2198_testshadhow.jpg.zip

[Danny Hays]

If I had to point out Vegas’s downfall, it would be it’s Chromakey pluggin. If I need real convincing keys I use Affter Effects with Keylight, specially with shadows, mainly floor shadows. Watch this video tutorial by Andrew Kramer on shadows. He also has a great one on keylight.

https://www.videocopilot.net/tutorials/3d_shadows/

There’s got to be a way to do this vith Vegas, at least with a flat floor. I’ll experiment and see what I can do. Oh yea, You would still have to use magenta back lighting to cancel out the green spill. Come on Sony, give us a good real keyer.