I have these really cool green screen effects that can be applied to a plane (they are videos), but I need to chroma key the green out of it so it only has the effects themselves. How can I do this? Thanks!
This is a simple node setup in Blender's Compositor. If you're unfamiliar with this part of Blender, leave a comment and I'll add step by step as to how to get into it.
If only wishing to remove the green and not overlay a background, i.e. have a video with just the effects, delete the BKD movie Node. Replace the Alpha Over Node with a "Set Alpha" node. Connect it as shown below.
You'll end up with an alpha layered output. If not needing the alpha layer, render in H264 AVI (RGB). (or your favorite format)
If you do want the Alpha layer, you'll need to render the video as a series of Alpha layered .png images. Make sure to create/select a special folder for these. There'll be a lot!
These can be compressed into a single file for storage.
I've found it easier if the key colour isn't as bright as it's shown in the top pic. (bottom of the keying node)
Getting the resultant movies onto a plane -
Simply texture the plane using "Generated" mapping for starters to see how it goes. You can revert to UV mapping if you prefer.
In the image properties "Image" tab, make sure to click on "Auto Refresh" so the movie or image sequence will play.
You can isolate a specific colour as long as you have good separation between foreground colours and background colours. This method wont be as accurate as the proper Keyer node available in the compositor and there are no blur functions to erode or dilate the mask. Also there is no easy way to add a mask shape to the key, unless you edit the geometry using a boolean modifier or some UV projection trick.
Here I have used the node Separate HSV to grab the hue channel. I tweak the input hue using a HSV node to target the green grass.
Finally I modify the alpha by increasing the contrast using a Ramp node.
*Note that I am using an emission node to make sure that there are no shadows, but you may want to cast a shadow on the background image.