6 Replies Latest reply on Jun 25, 2015 8:50 PM by adamneer

    Working with subtract option and a two masks

    media kat Level 1

      I’m trying to follow a tutorial on creating a shockwave like effect, and I’m having a hard time understanding part of the process. I’m working with 1080P footage.

       

      I did the following steps:

      - I created a new solid called shockwave

      - I right clicked on the new layer and chose pre compose

      - I renamed it shockwave pre with the default options

      - I selected the the precompose item in project panel

      - choose 960 x 960 for size for composition settings

      - I drew a circle in the center of the Composition window

      - I animated the mask expansion

      - at frame zero I made it a minus value so you can’t see white solid

      - I move forward a few frames

      - I set it back to zero again so the circle grows

      - I duplicated the mask

      - I  set the top mask to subtract

       

      This seems to make the whole solid in the background white. A large white square, and this is not what it is supposed to look like.

       

      What am I missing here.

        • 1. Re: Working with subtract option and a two masks
          adamneer Level 2

          You have 2 perfectly overlapping masks, one adding and the other subtracting, so they cancel each other out.  Sounds like you need to offset your keyframes so they aren't expanding at exactly the same rate and position.  Another possible problem is that if your first mask is set to subtract and the next is set to add, it won't do anything.  Add needs to be top in the stack, unless you use one of the intersecting options.

          • 2. Re: Working with subtract option and a two masks
            Rick Gerard Adobe Community Professional & MVP

            If you have two identical masks with one set to add and one set to subtract you have canceled out the mask completely. You have to have a difference in the values. I'm assuming you want to have a doughnut shape that expands to use as the source for your shockwave. There are two options. The first option would be to create two circular masks with one that is smaller than the other then animate the expansion. Since you've duplicated an already animated mask I'd select one of the masks with the selection tool (v) by double clicking to bring up the transform controls, then hold down the Alt/Option key and the Shift key to keep the transformation centered and uniform and drag to create your doughnut shape.

            Screen Shot 2015-06-25 at 6.23.22 AM.png

            The other option would be to use a shape layer with a single circular path with stroke applied. I would then animate the size and the stroke to get my growing doughnut. This eliminates the need to pre-compose for use as a track matte or source for displacement. You can even add repeaters to create multiple doughnuts from a single path.

            Screen Shot 2015-06-25 at 6.30.22 AM.png

            • 3. Re: Working with subtract option and a two masks
              media kat Level 1

              I'm just not sure why I am having a difficult time with this concept. I will try Rick's suggestion way next, though I'm trying to grasp this concept first. Please see attached if you can. Thanks.ae screen shot.png

              • 4. Re: Working with subtract option and a two masks
                adamneer Level 2

                Well the most obvious problem with your setup there is that you've duplicated the entire layer, instead of just duplicating the mask within the single layer.  An alternate suggestion that would allow you to leave your mask keyframes alone would be to set the mask expansion of your duplicate mask to something like -100.  So the first mask is set to Add.  Duplicate that mask, set to Subtract.  Then set mask expansion to -100 on that second mask.  This should give you roughly the outcome you're looking for.

                • 5. Re: Working with subtract option and a two masks
                  Rick Gerard Adobe Community Professional & MVP

                  Did you notice that I have the bottom mask set to subtract, not the top?

                  • 6. Re: Working with subtract option and a two masks
                    adamneer Level 2

                    Sorry, disregard what I said about modifying your mask expansion, I forgot that's what you used to animate the size.  (Although you could always just add the expression "value - 100" to your second mask expansion property, or even "n = *pickwhip to slider control*; value - n" to have a keyframeable offset size)