After Effects - Alpha Channel, Mask & Matte

all right in this tutorial we're going to look at an alpha Channel and how an alpha Channel is very important in compositing in layering objects on top of one another to complete a final composition an alpha Channel let's take a look here now for channel defines the visible and invisible parts of a graphic a graphic or motion graphic can consist of completely visible and invisible parts it can also contain semi opaque which means visible parts so I'm going to use a couple of terms here opaque means visible and transparent means invisible so something is transparent we can see through it something is opaque then it's a solid it's something that we cannot see through now there is going to be varying degrees between transparent and opaque and we're going to look at that so something could be 50% transparent which means we could see we'll be able to see through it and so we're going to take a look at that and a couple of other terms we're going to look at is when we create an alpha Channel oftentimes we'll create that alpha channel with a mask and a matte so we're going to be looking at that in this tutorial so first thing I'm going to do is I'm going to create a new composition just going to come up here composition new composition and just go with 1280 by 720 24 frames per second and we're going to leave this at 10 seconds and hit OK so we've started our new composition and now we're going to import some footage and some graphics that we're going to need to build this composition so let's go to right-click and go to import file and you'll be able to import these three graphics here they're PNG s and then we're also going to have a JPEG sequence up here in this folder that will import in just a minute but the first ones we want to get are these three PNG s back wall monitors and the table light and the thing about these PNG s as we import those they already have they were created in flash and they already have alpha channel information in them the back wall is completely opaque so it has no alpha channel information in it but the monitors you can see them right there and the table also those two they have alpha channel information well double click on them and take a look here and bring down our viewer size and bring it down a little bit more so we can see this you can see this black area here on this PNG represents the part of it that is invisible or transparent so we can see through all of this all of this black area and of course what you see here of course is opaque and then the same for the table we'll take a look at that real quick this area here is transparent that's our alpha channel information right there so you'll see how this begins to help us as we build our graphic so the first thing we want to do is we want to bring in this back wall bring it in and drop it into the composition and I know that the raster size of this you can look right here the information click on it and you see the raster size 38:39 by 2160 so that is much larger than our work area our composition area so we're going to scale that down we can click on that layer hit s for scale and that's going to bring up our scale property there and then we can scale this down and you'll eventually see yep the bounding box there so we can bring this down to about 36 34 percent and that fits it nicely kind of gets to the graphic the complete graphic in there leaves us a little going over the side there and that's fine so we've got our back wall that's our background there next thing that we want to bring in will be the monitors so let's click on the monitors drag them down and we want to drop it just above the back wall into our composition timeline and you can see once we get down there you get that black line right over the back wall so once we get that we can drop it in and of course take a look up here and see the raster size and it's 40 38 by 22 77 so we know that's much larger than what we need so we need to scale this down also so select it hit s4 scale and then let's drag that down and you'll eventually see the bounding box come in and you can kind of see the edges of the graphic so that lets us know that you see there how the graphic starts cutting off so we want to fit that in to make it look like it's fitting in the screen there so we're about around 32% on that now you can see how that alpha channel starts showing up or not showing up and you'd say that this graphic now fits over our back wall we're compositing here and so that alpha channel that alpha information right there is very important it is telling after effects that ignore all of this area there's nothing there nothing exists so that all we see is this graphic here and by the way these graphics were drawn and built by my brother al Waller just going to give him credit for that this was from a project he and I worked on together okay so we have the back wall our monitors in here and we also have now we need to pull in this table so click on that and again you can check the raster size there the resolution of it 33 52 by 497 so this is definitely much wider than what we need so we will scale it down once we get it in but let's click on it drag it in drop it on top also you can see how our arrow turns to a green plus button there once we get it in place and you can see that black line just above the monitors layer drop that in and now it is in there so we're going to scale this down again s on the keyboard will bring up our scale properties we can scale this down we're going to look at our width there you can see the bounding boxes come in and we're about 39% so that looks good but the position is wrong we want this at the bottom you'll understand this a little bit more in just a minute when we bring the footage in and start working with it so let's hit P for position with that table light PNG layer selected you can hit P that's going to bring up the position and of course the 640 is our x-axis and the 360 is our y-axis so let's click on the y-axis the 360 click on that y-axis and let's drag that down to the right dragging that down and let's just settle it about right there so our 640 by 633 is what the XY properties are on the position for that table like so again you can be see how we are beginning to composite this scene together and this is an alien spaceship the inside of an alien spaceship alright so we have again the Alpha Channel is showing up here and you can see the bounding box for this so all of this information is the Alpha Channel the mask that has been created for this nothing is again After Effects is that is seeing that alpha channel and knows not to put anything in there alright so we've got this scene coming together let's go take a look now and we want to import some footage so we can either double click in this empty area or right click I'm gonna double click it's going to bring open our box here and we want this MOV right down here after opening Thunderstone sino 406 so this is some footage we shot that is Thunderstone he is a puppet there and we want this footage so let's open that up and you can see he's in there and this is 1920 by 1080 these in this raster size resolution is a little bit larger than our composition and that was intentional so what we're going to do now well let's go ahead and bring this into the composition and we're going to drop it on top of everything at this point for right now so we can work with this footage so let's let's click on it and drag it down into the composition on top and you'll see now that Thunderstone is sitting there and everything else has disappeared it's not going anywhere but it is sitting underneath the Thunderstone layer and everything in here is fully opaque so that's why we are not seeing anything behind him but in just a minute we are going to work with that we're going to this is as you can see a green screen we're going to key him out and create some alpha information on this video clip and this is a video clip so I'll scroll through here and you can see that he is moving and talking and so we're going to work with that first thing I want to do though is let's scale him down a little bit so that he fits in and we'll position him also so hit s on the keyboard with your layer selected there and let's scale him down just a little bit bring those bounding boxes in see that and I think we're going at around 67% and that's where we need to scale him in now let's position him so you can hit P on the keyboard for position and we want to move him to the right just a little bit kind of Center him up and that will make more sense in just a minute once we start keying we'll bring this over a little bit and we'll adjust him a little bit in just some more in a few minutes once we get this key pulled all right we're going to look at green screening now and we're going to create some alpha information and we're going to use the terms that I looked at just a minute the first thing we're going to do is we're going to build a mask or we're going to create a mask around him something I'm going to do is preview I want to watch his motion and kind of get an idea of how much he moves in this area because we're going create a mask around him in just a minute and let's see how much he moves let's see I think for this shot he's not moving a lot so that's pretty good go with that what I'm going to do is let's make sure that that layer is selected in your timeline because we're going to create a mask and to create a mask we need the rectangle tool and the rectangle tool works in two different ways it will draw masks as long as a layer is selected or it will draw shapes with when there is no layer selected so right now we want to draw a mask and so make sure that that layer is selected click on the rectangle tool and what I want to do is we can give them a little bit of space we're going to come down here to just above the black bar and we're going to click and drag up to the right corner and yeah he disappears but as we click and drag he reappears in the area that we're drawing this mask all right so we can come up somewhere around like that let's preview that let's drag through and make sure that we've kept him all of his motion inside he he moves a little bit right there and he stays in that's good and keep on going through to make sure that he's completely in our mask so wait you see at this point I'm going to get my selection tool so I don't draw any more masks at this point because I am going to click around on this but as you see here we've already started creating some alpha information we have created this mask and it has cut out basically on our left and right side of the video and so now we're starting to see through this layer and we're going to continue to work on this so basically what I've tried to do is eliminate some of the area that we have to key in there was a light box over here that was hanging in the scene and of course we had the black bar down here that I didn't want to see and I think there may have been some other stuff over here so we've cut out a lot of the area that that we're going to key right now we don't need all of this out here so that's why we've started off with the mask now what we're going to do we're going to key the green out leaving nothing but Thunderstone in there and then we'll be able to finish compositing him into this scene so let's do that real quick select your layer here and we're going to go up to effects this drop down menu right here at the top effects and let's come down to keying so effect keying and what we want to get is key light key light one point two right here and when we select that that effect is now you'll see right here scroll that open you can see now that we've applied that key light effect to this layer something else hopefully you noticed is that our effects panel has opened up and you see that key light is right here now for this effect we're not going to need to set any keyframes in fact in this whole composition we're not going to set any keyframes whatsoever the only motion we're going to have will be Thunderstone and then some images that we put into the monitors in just a few minutes so let's finish up key light is our keying effect and we're going to start off very simply by coming here to the screen color it's set it black right now but we're going to select the color we want to key out the color we want to disappear the color we want to turn into alpha information we want it to go transparent so we're going to click on the eyedropper right here we have the eyedropper you can come come in to the green area and let's come kind of close a little bit close to Thunderstone actually let's come over here because I know this I've keyed this before and this kind of darkens over here so we're just going to try to get in between here where it's a little bit lighter to where it's a little bit darker that will just make it a little bit easier on our key we're going to click right in there and you can see now most of the green has disappeared and we have begun to create more alpha information now if you'll notice there's some just noise up in here this is left from the king and we're going to deal with that in just a second you can also see that we're losing a little bit of thunder stone down here he's becoming transparent and that is not what we want so we're going to fix that now remember I said that we first used a mask now we're going to create what is a matte and up here in the view where it says final result let's come down to screen matte and what that's going to show us is our matte that we're creating with key light the dark area the black area is of course the area that is dropping out the part that we're keying out the part that's going invisible the white area is the part that is visible and you can see that there is some difference here we want we want Thunderstone to be completely white and we want this area here to be completely black so we're going to make some adjustments to fine-tune this so we've checked screen matte right here that's what we're looking at so we're going to come down here to the screen matte settings in key light I'm going to scroll that open and the first thing we're going to do is we're going to clip this black so we can do that by clicking on the 0.0 click on it and start scrubbing to the right and then you'll notice immediately that we begin to clear clean up that black area and it becomes completely transparent so we're going to go with right at this point around 15 on the clip black so now we have the white area we want to deal with we want this white area to be completely white so we're going to clip the white now and it's at 100 so what we want to do is we want to clip click on that and we want to drag to the left to begin to drag it down and you'll see that our white area are the areas that's not completely white begins to clean up and we get more of a white area like we can get down around about seventy seventy two percent to clean that up and that's pretty decent so let's try that so at this point you can see we've cleaned up the black area the black area is what is transparent and the white area is what is opaque and we have created a mat now okay so we want to see the final result of this so let's go back up here to our view in key light and let's come down to final result and there we have it now there is one other thing I'm going to do just see if we can clean this up a little bit more the edges here a little harsh not too bad but I like to clean that up and what we'll do is let's just go with the screen soft and set it at about two pixels actually let's try three clean it up a little bit more just softens the edges a little bit but for right now when we could tweak on this a little bit more with with some of the other controls but for right now let's just go with that I'm just going to take a look at this and we're going to see what source does you can play with that whatever you choose there go with none for right now all right but what we have done is at this point we now have Thunderstone keyed out and again remember this is part of compositing if it wasn't for the mask we've created and now the matte that we have created Thunderstone that footage would not be usable okay so we have created alpha information and After Effects is recognizing that and so now we can put Thunderstone into this scene composite him into this scene and put him where we want to so I'm going to come down here just scroll this closed clean this up so we can see our layers and where I want Thunderstone is I really want him behind this table so we're just going to drag thunder stones layer belief beneath the table light layer that drops him in there and we can reposition him a little bit by just clicking on them and dragging now kind of setting him up and you can see where our bottom is the bounding box is showing us that and bring him in just a little bit underneath the table there so now we've got him composited in he's looking pretty good sitting there right in the middle of the scene where we want him so this is working so now we can scrub through kind of see what he does make sure he's a little off so that's where he's kind of starting so we'll drag him over a little bit more just kind of get him centered up in the scene maybe pull him down just a tiny bit more so his antenna up there are not jumping out of the scene and there we go so we've got him he's still scooting over to the side so drag him over a little bit more and I know when we start off he'll be a little to the right but he'll get back over to the left when he starts his lines and this is going to render out and then play we'll see how this looks here in just a second it has some audio but that's the scratch audio so it's not very understandable a few more seconds and we'll have him render it out all right so there you see again using the Alpha channel information in this image we have composited this scene together this special effects scene all right the last thing that we've got is we want to put something in these monitors so we're going to go and import one more graphic or one more video piece of video footage and if you've lost your project panel up here it could very well be hidden right here behind this double area double arrows right here and we click on project and now we have our project panel back with all of our footage and graphics in here and our compositions in here so we're going to need to import one more piece of video footage so let's double click or ctrl I or file import and this is a JPEG image sequence so if we look at this it looks like it's just a bunch of JPEGs and that is correct it's just a bunch of JPEGs but these JPEGs are all numbered when we tell after-effects to recognize this as a JPEG sequence what is going to do is it's going to count each one of these JPEGs as a frame of video and it's going to basically so all these together or melt them all together into one complete video file so it won't be a ton of JPEGs that it imports you can see there's 360 of them there it will not import 360 separate JPEGs but what it will do is import them all together as one video file so click on the first one make sure that JPEG sequence is selected down here and then you're ready to import that in and you'll see here that it is represented as a JPEG sequence or at least a sequence of images and it is if we double click on it you can see it right there and scrub through you can see that it's about 12 seconds long and it does have motion in it along with the images changing there in the middle alright so this is what we want to put in our monitors so let's close this out right here come back to our composition and what we want to do is we want to drag this down into our composition and let's drag it behind our monitors and drop it there drop it below the monitors layer and you'll see now we've got this large image in the background there and that is not what we want we want it to fit inside of here so the first one I'm going to work on is the left and you can see already that what we need to do is scale this down some so let's hit s select your layer and hit s and then let's scale this down a bit let's get say around 30 let's just try 33% at this point then let's click in here on the image and drag it over behind this left monitor so it's going to be needed it's going to need to go up a little bit larger than 33% probably 35% try that that works good okay so we have the image in here and you can see right now it doesn't look very good because it is poking out behind the monitor so we are going to one more time create alpha information by creating another mask now this time we're not going to use the rectangle tool or the rounded rectangle ellipse or any of those we're not going to use any of those tools to create a mask this time we're going to use the pen tool and this is will take just a few seconds let me explain it to you and you can follow along with this and then I'll go over it again so what we're going to do is we're going to click we're going to first go and click on get the pen tool and we're going to use the monitor as our guide as to how to draw this mask but what we want to make sure is that we're drawing the mask on our IRC lair there okay so make sure that that stays selected but we're going to it's going to look like we're drawing it on the monitor here but it's actually going to be applied to the mask is actually going to be applied to the IRC that video clip back there so make sure it's selected and then what I'm going to do is if you will just watch me on this first time around because what we need to do is we're going to draw a path and then once we close it at the very end it becomes a mask and what we need to do is come back to our beginning a point so right here I'm going to I'll just start right up here this will be my beginning point so I'm going to click I'm not clicking a dragon that's clicking letting go coming in a little bit clicking again clicking again and I'm just clicking these points as you see there are lines connecting these points and I'm starting to draw my mask I'm going to keep coming around and come up here and then I need to close this out right now this is an opened path and I need to close it to make a mask and you can see there at the end of the pen tool you can see that it turns into a circle when I hover over that beginning position and now I'm just going to click to close it and when I click and close it it becomes a mask and you can see now we have cut out the outside of that image and so now it appears to fit directly inside of the monitor you would never know that it was another graphic that was just hanging outside so again we have created another mask just like we created one around Thunderstone but this time we've used the pen tool and we started off here we clicked on around until it came to the end and we closed it out now to show you that mask it is right here on our IRC lair we're going to open that up and there's that mask one so we've created that mask now I'm going to go through this process one more time just to demonstrate it again because a lot of times we miss the fact that we need to close this out so I'm going to delete this mask and I'm going to start over so you see there's the image again I'm going to make sure that I'm selecting that image that I want to draw the mask on and then I'm just going to start clicking and dragging click once move your mouse move the pin tool click again click again just keep clicking around until we get back up to the beginning and you can see again at the end of the pen tool there when I come to that beginning position is telling me that circle there is letting my letting me know that I'm about to close this out and that this will be a mask so click on it we close it out it's a mask now and we have masked out this outer portion of it and now we have our image inside of the monitor all right so what we need to do is we still have one more monitor over here that we need to do the same thing with and all I've done here is zoomed in on my canvas let me go back out to under present and reposition and we are going to I'm going to clean this up just clean up scroll that closed and I'm going to drag another instance of this footage into the composition and I'll drag it below the monitors I'm going to drag it below the other version of it the IRC and just drop it in there and you can see again and just so I'm not clicking I'm going to go to come over here I have the pen tool you can see and I want my selection tool so I'm going to select the selection tool right there you can see that the image is like it was originally so what we need to do again is scale this down so s on the keyboard scale this down I don't remember what it was I think it's 35% so we can just get scrub it down or we can type in select in one of the extra Y position and type in 35% and then once we have that we can come over and actually for this one because the angle is different we're going to actually need to scale that one up a little bit more so let's try 37% so that it fits in there completely alright that looks good so we've positioned it and now we need to draw a mask so remember select the layer that you want to draw the mask on get your pin tool and then come up here and begin to draw your mask and just click go to your next point click and just continue to do that on around the image until you come back to that first point and you close out your path and make it a mask and there it is again there's my beginning point I'm going to click into it close it out and now there's the mask so we have now composited this scene together completely and we have used a mask a matte we've created alpha information we've keyed out we've done some green screening we've keyed out Thunderstone so we've used an alpha Channel mask and an alpha Channel mat to create this scene all right there you have it alpha channel mask and matte

Channel: Lee Waller

Views: 28,926

Keywords: After Effects, Motion Graphics, Motion Media Design, Alpha Compositing, Matte

Id: 0_lDNqv7-D8

Length: 31min 57sec (1917 seconds)

Published: Mon Sep 28 2015