6 Replies Latest reply on Feb 18, 2012 4:26 PM by lmaclanphere

    revealing/masking linework

    lmaclanphere Level 1

      hi all


      I'm trying to achieve a certain mask effect...


      I have a curved line, in the shape of an infinity symbol--I also have an object traveling along that curve, and I want a mask that will reveal just the portion of the curve that trails behind the object;  make sense?


      I know that the write-on effect has this capability (time length, in seconds I believe, to reveal then hide) but the problem comes at the intersection of the infinity curve--the write on will reveal the curve it's crossing perpendicular as well, and I don't want that. Just want to see the single curve trailing...


      what about the basic stroke effect?  is that an option?


      thanks very much for your ideas!



        • 1. Re: revealing/masking linework
          Mylenium Most Valuable Participant
          what about the basic stroke effect?


          Sure. Simply copy&paste your object motion as a mask on a comp-sized solid as a mask and set the mask mode to none, then reference the mask in the effect... You can of course also use particle systems for any kind of trails...



          1 person found this helpful
          • 2. Re: revealing/masking linework
            lmaclanphere Level 1

            thanks!  but that went over my head just a bit


            my motion is tied to a null object; so I copy paste the position keyframes on the null, I create a new comp size solid, then....?



            • 3. Re: revealing/masking linework
              Dave LaRonde Level 6

              Here are some EXTREMELY basic, AE 101-type questions:


              If you're using the write-on effect as a track matte to reveal an existing symbol, you should know that the brush position property gets its data from the comp coordinantes.  Have you precomped your symbol and created the mask path on the precomp?


              To compensate for revealing too much of the symbol have you either adjusted or animated the Brush Size property in Write On?


              For the object moving over the symbol, have you tried pasting the mask path data you created earlier into the object's position property? 

              Both Write-on and position animation will start at the same place, the initial mask path vertex.


              Why do you feel the need to use a Null Object?


              If any of these questions have you stumped, you really need to visit this page.

              • 4. Re: revealing/masking linework
                lmaclanphere Level 1

                thank you--  I hope I don't need to go back to the drawing board though!  --I'm just looking for a more elegant solution than fiddling with the write-on (yes, I am aware that you can adjust brush size).


                I am confused about copy/pasting motion data onto solid/mask layers, and I want to learn more about that, even if I could have solved the problem already with a different method;



                • 5. Re: revealing/masking linework
                  Dave LaRonde Level 6

                  Go the layer with the mask.  click the stopwatch to make a mask path keyframe. Highlight the keyframe and copy.

                  Go to the layer you want to move.  Open the Position property.  Make a keyframe. Highlight it and Paste.  The mask path comes in as a 2-second position animation.  You can change its length to match the length of the Write On animation, where you use the exact same trick to animate the brush position.

                  • 6. Re: revealing/masking linework
                    lmaclanphere Level 1

                    thanks Dave, but let me clarify the setup: 


                    there are no mask layers anywhere; there is just the motion on the object--which I have achieved by copy/pasting my infinity symbol curve (from illustrator) onto the position attribute of the object-- I got rid of the null which I now realize was not needed.


                    so I've got my little object moving along the curve nicely, now I need to figure out the mask part...


                    what do I need to add or do to follow your above instruction?


                    thanks again