4 Replies Latest reply on Sep 22, 2009 5:19 AM by ingvarai

    Grouped masks and how to exclude layers from adjustments

    ingvarai Level 1

      Here is my scenario. I have two shots, one is of a bench, leaning against a wall. My second shot is of a couple, shot against a green-screen.

      I layer these shots, giving the impression of the couple sitting on the bench. I have no problems with the green-screen technology, all is fine.


      Now, I want to give the impression of the sun partly shining through the leaves of a tree, so I have two questions regarding this:


      1) Is there a way to "group" masks? I want to make a lot of "holes" in an adjustment layer, resembling the blurred shapes of leaves, then animate this, simulating the wind in the tree branches. Basically, I can make it work, but I would rather have one single mask, than 50 masks. Can I use a Photoshop file, with an alpha channel? Using such a mask, and adjust brightness and contrast, and animating this mask, I would probably become a rather realistic impression.


      2) I want to use the same mask on the lowest layer, the layer with the shot of the bench against the wall. However - here comes the challenge, I must offset the mask, since the shadow on the wall for obvious reasons cannot align prefectly with the shadow on the heads of the two people. I have found no way to "aim" the adjustment layer to selective layer(s), to prevent an adjustment layer from applying its adjustment to all layers below.


      If I can avoid using precomp, I would be happy, because I think when using precomp, I will not be able to test the effect immediately. (Please correct me if I am wrong here). Lastly - I ask this question mainly because I want to learn more, solving this issue in particular is of second interest. I am rather new to After Effects, by the way.



        • 1. Re: Grouped masks and how to exclude layers from adjustments
          yenaphe Adobe Community Professional

          First of all, no, you can't merge all your masks into one. You can of course use a file with an alpha channel.


          And no, there is no way to aim your adjustement layer on specific layers, you'll have to precompose. Precomposition will not have a huge impact on AE speed, so you can make a lot of them without noticing any speed change.

          • 2. Re: Grouped masks and how to exclude layers from adjustments
            Rick Gerard Adobe Community Professional & MVP

            There are a couple of options for you here. Probably the most effective would to to relight your scene like it was a real scene. Separate the bench from the background, create a wall and floor, make your bench, background and keyed actors 3D layers, add some ambient light and a spot light, then put a gobo between the spot light and the actors with the material properties set to cast shadows only. Then adjust the light transmission of the gobo and the values for shadow diffusion and light intensity to get the results you want.


            The gobo could be created in Photoshop, from a solid with masks, with vector paint... just about any way you want as long as you get a layer with a bunch of oddly shaped holes in it. Without seeing your bench background shot I can't tell you the best way to separate it from the background and create a wall and floor layer to accept the shadows. You might want to check out Photoshop's Vanishing Point tools.


            Here's a CS4 project I whipped up to demonstrate the technique of lighting with a gobo.

            1 person found this helpful
            • 3. Re: Grouped masks and how to exclude layers from adjustments
              Mylenium Most Valuable Participant

              You should not see pre-composing as a limitation or workaround, but rather a way of structuring your workflow and a means to control rendering order. There's nothing wrong with using it and contrary to your assumption, there is nothing that stops you from checking your result immediately. That's what multiple composition viewers and timelines are for. Just use the little lock symbol to assign a viewer permanently to a comp, then from the flyout menu in the top right corner add a second viewer. Multiple timelines can be created by simply arranging the tabs into separate panels. Assuming, you have the Synchronize related items option enabled in the prefs (it should be by default), that way whenever you change something in one comp, it will update in the other comp. Another alternative might simply be to use shape layers instead of conventional masks They do not really act liek a unified shape, either, but offer ways to merge and combine individual shapes plus have parametric animation options, which should greatly help getting exact windows, blinds or more random shapes. Rick's suggestion of using AE's 3D features is spozt on, but of course if you are really just worried of about transforming your shadow, using Corner Pin, Transform and other distortion effects might work just as well in combination with the Multiply blending mode.



              1 person found this helpful
              • 4. Re: Grouped masks and how to exclude layers from adjustments
                ingvarai Level 1

                Thanks a lot! I did learn a whole bunch of new things, yes I did. And I understand that I will not master After Effects the first couple of weeks.. What I learnt, and what was a milestone for me as an AE beginner, is that I can use an alpha channel bitmap to dictate how AF applies effects. That alone was worth this discussion.


                What I did - I created a separate Comp with the footage from bench leaning against the wall (a wooden red wall). I then created an image in Photoshop, totally black, I then had a transparent background, and used the eraser with the shape of a leaf and punched many partly overlapping holes in it.

                I then used this image above an adjustment layer, setting the adjustment layer's track matte to alpha matte. I added a brightness/contrast effect to the adjustment layer, reducing brightness by 33%. I also added a blur effect to the image layer with the leaves.


                Now, I animate the image layer with the leaves, slightly back and forth, using the "Ease" option.

                Having done this, I duplicated the two layers, to get the same effect a second time, but this time I changed the size of the "leaves image" slightly, and I animate it using a different direction and a different speed. This way I get two layers of leaves moving back and forth, and two layers overlapping each others partly using a random pattern. The result is so convincing, you won't believe it!


                When it comes to lighting, I did make the layer with the couple 3D and I did use lights and I think it looks ok, but still I am not sure what I really did :-) There is a lot to learn here for me, obviously. Anyhows - the result, from starting with Keylight for the green-screen, through my latest efforts with the leaves, is way beyond my wildest expectations!


                I am looking forward to my next "impossible task" which later will turn out to be routine for you expert guys who hang out here. I will study your posts later and see what I can learn more.