9 Replies Latest reply on Apr 5, 2013 10:29 PM by Rick Gerard

    Problem with mask

    Herugrim123 Level 1

      I am currently editing a video of a play in which the cast dropped fake snow which looked great for the audience but, unfortunately, is not visible to the camera. I have added snow using Particle Playground's Cannon exploder which looks great but it should not be falling on the audience's heads ! I have added a mask to the snow layer but is not hiding the snow. I can't understand why not. I've tried leaving the condition at "add" and ticking the "inverted box and leaving the "inverted" box empty and changing the condition to subtract; but the snow is still visible inside the mask. Does anyone know what I'm doing wrong ? I have used masks before without any trouble...help ! btw I am using CS5 on Win 7.

       

      Regards,

       

      TL.

      mask example.JPG

        • 1. Re: Problem with mask
          Klaus_Brandenburg Level 2

          You need to precompose your particle world layer (move all attributes into new composition) before you can apply a mask to this effect.

          • 2. Re: Problem with mask
            Herugrim123 Level 1

            Klaus, I copied and pasted my Particle Playground snow layer into a new comp and redid the mask ( just to be sure ) and pre-rendered it and the mask is still not hiding the snow ???

             

            Regards,

             

            TL.

            mask example 2.JPG

            • 3. Re: Problem with mask
              Szalam Adobe Community Professional & MVP

              Bring your snow composition into the main comp and apply the mask to the snow composition inside the main composition. You should not be applying your mask inside the snow composition.

               

              This has to do with the render order of After Effects. Many effects will not respond to masks because they're working on the alpha of the layer and whether or not there's a mask, doesn't matter. A composition, however, is treated just like footage. Therefore, if you have a composition containing a layer with your effect on it, you will be able to apply a mask to the composition.

              • 4. Re: Problem with mask
                Klaus_Brandenburg Level 2

                That's not exactly what I suggested. Starting from your original comp, precomp your particle world layer (move all attributes into new composition), then go into that precomp, copy the mask (and delete it here) go back in your main comp and paste the mask to the precomp. now the particles should be cut off.

                • 5. Re: Problem with mask
                  Herugrim123 Level 1

                  Thanks for your help guys but I couldn't get it to work the way you were suggesting. If I took the snow layer and made it into it's own comp, when you import that into the main comp, the transparency was gone so that you just see snow on a black background ! I didn't touch the default settings, one of which is RGB + ALPHA. Maybe I should have done something there.

                  In the meantime, I found a work around where I made a new audience layer and cropped just the audience and put that on top of the snow layers. I'd still like to understand what I was doing wrong though....

                   

                  Regards,

                   

                  TL.

                  • 6. Re: Problem with mask
                    Herugrim123 Level 1

                    Okay, I made a new comp of the snow and managed to import it into the main comp with the transparency intact, but when I add a mask to the snow comp layer, it still doesn't mask ???

                     

                    Regards,

                     

                    TL.

                    mask example 3.JPG

                    • 7. Re: Problem with mask
                      Rick Gerard Adobe Community Professional & MVP

                      Your screen shot has been reduced in size so much that I cannot read anything on this computer but I'll give this a shot. I think that you didn't move the snow effect into the pre-comp. If you reveal the Effects Control Panel do you still see Particle World?

                       

                      Here's what I would do.

                      1. Duplicate your footage
                      2. Add a black solid above the top copy of the footage
                      3. Change the blend mode of the black solid to screen
                      4. Draw and if necessary animate the mask so that it follows the audience movement
                      5. Set the black solid as a track matte for the top copy of the footage
                      6. Add a new solid to the comp and put it just above the bottom audience footage
                      7. Apply your snow effect to that footage.

                       

                      Now you've got a layer of just the audience over a layer of snow effect over the original footage. Experiment with blend modes for the snow layer and you should be done.

                      • 8. Re: Problem with mask
                        Herugrim123 Level 1

                        Thanks Rick, That all worked okay. I didn't even think of using blend modes but I will in future ! Incidentally, the screen shots are poor because I had to downsize them to meet the requirements of less than 450px high.  I could make the screen shots of less of the screen but I find that those looking at them don't then have all the information.

                         

                        Regards,

                         

                        TL.

                        • 9. Re: Problem with mask
                          Rick Gerard Adobe Community Professional & MVP

                          You don't have to downsize your shots. The forum will limit the size with html coding in the thread but they will appear full size up to a limit of 2.0MB in the popup.

                           

                          Glad I could help.