Chroma Keying & Lightwrapp

Some time ago I showed you the chroma key I purchased. I've used it a few times already and now I wanted to share with you how to make a green screen removal in Blender :) In the tutorial, we'll go through the process of removing the chroma, and then I'll apply a lightwrapp, which is a technique that allows the background to affect the edges of the foreground, achieving a better integration between both of them. 

Watch this video on YouTube

Download the photo of me being awesomely serious in front of a green screen to practice with it :)
Download the background painting I used in the tutorial.

Now I think it's a good time to write a little about chroma keys:

- What are they used for?
Chroma keys are used to place behind the stuff you want to be there in the final video (like actors), and it's all with the same color, so later you can pick that color and convert it into transparent. It's very useful as otherwise, you'd need to mask your actors manually frame by frame! Imagine rotoscoping your actors hair 30 times per second... not cool, right? :D A chroma key helps a big deal with that task! :D

- What colors should I use for my chroma?
Well, you can use any color your want, you just need to keep in mind that you should have a color that is not present in the foreground (actors). For example, if you look at the lord of the rings, a lot of times they used blue screens: this is because they were in forests, which means that a lot of green color is present in the foreground. The thing is to have your screen in a very different color, so when you remove it, it doesn't take with it parts of the foreground as well :) Usually, the most used colors are light green, blue and magenta, but if your actor is a ninja, with a full black costume, it would be nice if the screen is white :)

​- Should I apply a good lighting to it?
Of course, if your chroma is well lit, it will be much easier to remove it. The more uniform the color is, the faster is to select that color. In the other hand, if you have some creases producing darker areas in your chroma, it'll probably take some more time to get rid of it. You may even want to use two different keying nodes for the darker or brighther spots of the screen. If some parts go close to black or white... then you might have a little problem, as they may have some similar tones as in the foreground, which is not what you want, trust me :D So... yes, you can achieve a cool chroma keying without a perfect lighting, but if it's well lit... it'll be much faster and easier!

I hope you found this interesting! See you! :D





excelente Oliver. Quería preguntarte qué documentacion consultas para saber lo que hace cada nodo y todas sus opciones. Tambien los modificadores, y demás. La info que sale en la wikipedia no da tanta información. Gracias y enhorabuena por tus magníficos tutoriales.

Gracias, Richisan :) Normalmente me dirijo a la wiki de http://wiki.blender(dot)org/index.php/Doc:2.6/Manual (Sustituye "(dot)" por un punto).
Normalmente todo suele estar ahí, luego ya trasteo con las opciones hasta que comprendo bien lo que hacen. Otras veces es cuestión de práctica :P

Very good tutorial. I am thinking how to limbs in direct contact with the background, like a leg directly in contact with the floor, in this case the floor is background. And it seems I was interested to see the tutorial in the video or animation. Thank you.

With contact areas it works well... as long as you have a quality chroma and such, otherwise, the shadows on the ground can become an issue. About video or animation, it's just the same as for a single frame, if you press play it keeps working along the footage (you may need to retouch some little parameter depending on your video if the lighting conditions or something happens in it).