Mask on a plane?


Just started using HitFilm Express last week, and I'm loving it. However, I am stuck and if someone else has asked this question, please let me know. I just couldn't figure out the best search terms.

I created a plane for Lightning and Electricity, then set the Blend to "add." However, I am trying to mask some of the lightning (see link) to appear as if its behind my subject. If you look at the screen shot, you'll see I created the mask, but for some reason I can't get it to mask part of the lightning so it's not on top of the subject.

Should the mask not be created on the plane? Let me know if the question doesn't make sense.

Thank you in advance!



  • Triem23Triem23 Moderator

    It's an order of operations thing.

    Individual layers render from the bottom of the stack to the top. 

    Everything on an individual layer applies top to bottom in that layer's controls. 

    So, the Masks are applied before effects. The Lightning effect renders after the mask, so the mask is ignored. 

    Now look at a Grade Layer. The order of the Controls modules is different. On a Grade Layer Masks apply after Effects.

    So,the easiest solution is to put the Lightning on a Grade Layer instead of a plane and mask that. Another option is to put a copy of the video over the plane and mask in the portions of the actor in front of the lightning. 

    Grade Layer is easier.

    Just lock in your brain that the layers render bottom to top, the individual layer works top to bottom in the Controls panel. Knowing the order of operations will help you plan and or troubleshoot. 

  • The other nice thing about using a Grade Layer is that you won't have to change the Blend Mode. Grade Layers are naturally transparent.

  • Triem23Triem23 Moderator

    @FilmSensei to be pedantic a Grade Layer is a forced render of all layers below itself. Not quite the same thing. 👍

  • @Triem23 That's true... just don't put anything underneath it! 

  • Triem23Triem23 Moderator

    @FilmSensei I teasingly suggest you'd not had your coffee before your last couple posts. Usually you're spot on. However, in this case you goofed a second time.

    @neorpheus (great screen name, btw) in this case you do want something under the Grade. The video you want to mask around.

    To recap the thread - lightning on a plane (or photo or video layer) is calculated and rendered after masks are applied, so the lightning won't be affected by masks. 

    A Grade Layer forces a render of all layers below itself. The raw state of a Grade Layer is that render. The render then goes to Effects. The practical effect is a Grade applies effects to all layers below itself. The order of operations on a Grade is different than other layer types, so a mask on a Grade does affect effects. In this case you can roto around the your actor and other objects.

    The Lightning generator has its own Blend Mode. Consider setting the Blend of the Lightning to None and the Blend of the Grade Layer to Add - just like the plane you tried. 

    A Grade being a render of layers below has other implications. Any effect that uses a "Source Layer" can use a Grade Layer as the source. This is often useful - it doesn't apply to your question, but it's one of those things you should know.

    As an example, in the shot below I had used a Light Wrap effect on the TARDIS model. If I used the video as the Source Layer the pavement would be lighter than the TARDIS and I'd get a light halo at the bottom of the TARDIS. So I put a copy of the TARDIS (invisible) with a "shadow catcher" and light above the video and below a Grade Layer. Using the Grade as the Source for the Light Wrap "baked in" the cast shadow removing the light halo at the bottom of the TARDIS.

  • @Triem23 Sorry about that... The first one was a goof, the second one was a joke (albeit not a very funny one, apparently). :)

  • Triem23Triem23 Moderator

    @FilmSensei without facial expressions, body language and vocal tone sometimes jokes are hard to spot. 😊👌

  • @Triem23 ; @FilmSensei ;Thank you so much for the information!! I didn't get any time on Hit today, but I will give this shot tomorrow night and report back!


    Thanks for being so helpful to a noobie!

  • Triem23Triem23 Moderator

    👌👍@neorpheous everyone on the Forum was super cool to me as a n00b. Just passing it on. 😁

  • edited July 25

    @triem23 success!!! Thank you for the tip!!

  • Triem23Triem23 Moderator

    @neorpheous looks good! 👌👍

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