[ANSWERED] End Credits Crawl doesn't work with masks

edited April 27 in Express Support

On a whim, I decided to play with the End Credits Crawl effect, specifically to see if I could create a look I've seen occasionally where the top and bottom of the credits are masked (guessing) to fade in and out gradually as the credits scroll.  I thought it would be fairly easy, but it turned out to require more steps than I expected.  I'm doing this in HitFilm 4 Express version 4.0.0146 (Update 8) on a Mac Mini running OS X 10.10.5.

My test was rather simple. In a new comp, I made two colored planes, both black, and dropped the End Credits Crawl onto the top one.  After playing with the effect settings to get several lines of text crawling up the screen, I then zoomed out a little and made a rectangular mask on the top plane that was wider than the comp dimensions, but shorter vertically, so that there was a clear gap between the top and bottom of the mask and the edges of the comp frame.  I planned to feather the mask next, but I already noticed the problem: the crawl text wasn't being masked.  Here's a screenshot showing the problem (with the lower plane hidden):

End Credits Crawl masking bug

The crawl text should cut off where the plane is masked, but for some reason it continues beyond the mask.

Long story short, I was able to get what I wanted by taking advantage of this bug (I'm assuming it's a bug) and doing a workaround.  I took this plane with the crawl and made it into its own comp.  In that new comp, I shrunk and moved the mask so that it was completely out of frame, leaving the crawl over a transparent background.  Back in my original comp, I masked that embedded comp as I had originally planned, and got what I wanted:

I'm guessing this is a bug because my assumption is that any effect applied to a plane layer should be affected by masks added to that layer, so I was surprised when this wasn't.  If this is the way that the crawl effect is supposed to work with masks, could someone please explain why?

Comments

  • Triem23Triem23 Moderator

    Long story short, not a bug. Exactly how Hitfilm is designed to work. 

    23:10 in this video goes over the order layers render. For planes masks are applied, then effects, then transformation. Planes need effects to draw over masks or you wouldn't be able to (for example) mask an object and have it glow. 

    https://youtu.be/1Oi8Kkn_qZ4

    What you ended up doing is actually pretty much how it should be done when you want masks after effects. 

     

  • edited April 27

    @jsbarrett

    [Edit - Triem23 posted while I was still typing]

    It's because of the order of operations.

    You've probably noticed that Hitfilm applies the effects from top-to-bottom, in the order you placed them. But more than that, it applies all the things above "effects" (including masks) before it applies the effects. So it applies the mask, making part of your plane transparent, and then adds text to the whole plane (including the transparent bit).

    Obviously what you actually want it to do is to is to add the text effect before the mask, one way to achieve this is using an embedded comp (like you did), another way is to add the mask to a grade layer above your plane, (or just to add both the effect AND the mask to a grade layer, since grade layers apply effects before masks) but this will apply the mask to all the planes below the grade layer as well, so in order to actually use it you would still need to put the whole thing in an embedded comp anyway...

  • Triem23Triem23 Moderator

    @JMcAllister well, with Hitfilm if it's not doing what you think it should be doing, putting it in an embedded composite shot is usually the fix. Lol. 

  • Thank you both for the clarification.  I've been meaning to watch your HitFilm tutorials, @Triem23, but haven't had the time.  Might as well start now. :)

  • @jsbarrett they are long, but detailed and worth a watch to really understand what goes on in Hitfilm. Mike has a pretty good handle on how things work.

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