In a world of green screen technology, I just though I would be useful and show everyone how to make a green screen using nodes. Notice, this method is used for layering a live shot green screen video on top of another. i just really donât have time or money to set up a green screen.some images would take up too much space on a page so just click on them.
Donât delete the default cube or anything when you open up blender, as we will use it for our green screen image. the background color in the 3d render is automatically transparent, but as you will see later, if you do the tut properly, green objects will not show up in the render which obviously means they would not show up in a live video. First, click âset compositeâ in the render buttons in the buttons editor:
Press â0â in the 3d view to go into the camera. Now, right click on the line separating the buttons window and the 3d window. Choose âsplit areaâ and click where preferred to split the area:). It should preferably end up looking like this:
http://img520.imageshack.us/my.php?image=firstoneia0.png
now click on the right window for the node editor:
http://img68.imageshack.us/my.php?image=2ndonefw7.png
at the bottom of the panel there is an image of a face. click on it:
now click the button that says âuse nodesâ and it should end up looking like this:
also, draw a box where it shows in the image to delete the connection. Press space now to open up a menu and do âaddâ then âinputâ then âimageâ
I am going to select a video, because images can be still and boring in a green screen movie. It ends up looking like this:
now click on the picture of a face and select âmovieâ
Itâs only going to display the first frame of the movie, so you should figure the number of frames in your movie. go to the ânode editorâ and input that number of frames where it shows in the picture:
Now press âspaceâ to open up the menu, then do âaddâ then âmatteâ then âchannel key.â It should end up looking somewhat like this:
notice that the setting âGâ (for green) is enabled. set the âHighâ and âLowâ setting all the way up and attatch the yellow image dot to the output as you see below. Right now you wont see anything amazing, but the fun is about to start:D.
Right click the default cube, and go to the âmaterialâ settings. click âadd newâ to add a new material to the cube.
change the material color to green and press F12 to render the image. It doesnât seem to be amazing at all, but close the render window, and you can see that in the ânodesâ window, the GREEN cube is transparent.
press the arrow at the top left of the âchannel keyâ box to compact it down. This just saves space as you will not need to use it anymore.
Press âspaceâ yet again to open up the menu. Go âaddâ then âcolorâ then âalpha overâ
It would probably look like this. If it doesnât, connect everything to look like this:
now hopefully, you havenât forgotten about the video at the top left. If you did, thatâs just too bad:). But for all of those who did not, connect your nodes to look like this:
now press F12 to render. It should look somewhat like this:
not really what you expected, but wait, go to the 3d view, add a normal cube, and press âgâ to move it to another part of your cameraâs view range. it should now look like this:
Unfortunately, there is a blue silhouette around each image. this would not show up in a live shot green screen movie. However, if you want to take it away, go the the âalpha overâ in the node editor, press the âconvert premulâ button, and put the âpremulâ factor all the way up:
now go to the âworldâ buttons in the âmaterialâ buttons and set the background to be white:
Render the image again and you will have gotten rid of most of that annoying blue silhouette.
NOW, FOR ALL OF YOU PEOPLE WHO HAVENâT READ THE TOP PART OF MY TUT, GREEN OBJECTS DO NOT SHOW UP IN THE RENDER WITH THIS NODE SETUP. Also, green objects are very useful for hiding other objects behind:
unfortunately, there is a tiny trace of white in the image. to get rid of all the white, go to the render buttons (F10) and enable âpremulâ
use this method for layering a green screen video on top of another video. However, considering green screen live videos usually donât have perfect green you may need to edit out a few annoying black specks. to do this, do âaddâ, âmatteâ then âluminance keyâ and attach it to the channel key. play around with it and all black specks will be erased:
http://img165.imageshack.us/my.php?image=greenscreennospeckxo0.png
Congrats, you have successfully made a green screen using nodes. If you know how to animate, then this is an easy way of making a video.
by the by, if I overlooked something in this tutorial, or if you have a problem with it, donât hesitate to tell me.