Explosion behind a moving person.

So I am trying to create a scene where an explosion occurs behind a person who is center frame and walking towards the camera slowly. I duplicated the footage layer, and masked the person in the top footage layer to allow the explosion to look as if it occurs behind the person. However since he is moving the masking does not look great. 
How would I remedy this problem?

Comments

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,219 Ambassador
    If the camera is not moving and you have a clean plate of the background without the actor, you can try the Difference Key effect to get a cleaner mask. Otherwise, you're just going to have to manually refine your roto mask.
    Now... Besides the explosion element, remember you can add glows to blend the edge. Maybe light rays, and maybe a light wrap effect on your masked actor to bleed some of the explosion color onto him.
  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,219 Ambassador
    Ooh, and what Win said would make any glows etc look like light wrap on the actor. Good call.
  • KirstieTKirstieT Staff Administrator, Moderator, Website User Posts: 1,053 Staff
    It's amazing what you can do with a mask, feathering and a bit o'glow!
  • ChrisMurphyChrisMurphy Website User Posts: 61
    Thanks! I will try these techniques. I should have my movie done with in the next few days, so you can check it out.
  • ChrisMurphyChrisMurphy Website User Posts: 61
    edited April 2014

    Quick Question! So instead of duplicating the footage layer, then putting that above the explosion layer, and then  masking the top footage layers subject. What would I do now, to achieve the masking of the explosion technique that Win desrcibed. 

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,219 Ambassador
    Just use a mask on the explosion layer. Change the mode of the mask from "ADD" to "SUBTRACT."
    An "add' mask means" show what's in the mask." A "subtract" mask means "hide what's in the mask."
    On the "Support" page of this forum (button at top-right of screen) there's an excellent tutorial on masks by Axel Wilkinson that may be useful. He covers all the different mask modes and shows you how to combine masks for more complex effects.
  • ChrisMurphyChrisMurphy Website User Posts: 61
  • ChrisMurphyChrisMurphy Website User Posts: 61
    Its strange though. Everytime I change it to subtract the explosion completly disappears. Is the explosion to be the top layer?
  • ChrisMurphyChrisMurphy Website User Posts: 61
    Not sure why everytime I put it on substract the explosion completly disappears
  • ChrisMurphyChrisMurphy Website User Posts: 61
    Thanks so much!
  • ChrisMurphyChrisMurphy Website User Posts: 61

    Just keep it on add?

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,219 Ambassador
    Yeah, leave the mask on ADD, then check "invert mask."
    Sorry for the incorrect information earlier. I tend to work un creating greyscale elements for luma keys rather than direct masks, and forgot keys work a touch differently from masks.
    Lets resummarize: put the explosion over the actor. Animate the roto mask on the explosion layer (if you have the mask from rotoing the actor, you should be able to copy/paste your old mask.) Leave this mask un ADD mode, then invert the mask. This should punch a hole in the explosion. Now apply some glows and/or gleams and/or light rays to your explosion layer, which should help cover any errors in the mask roto.
    Good luck!
  • ChrisMurphyChrisMurphy Website User Posts: 61
    I got it to work! Looks Great!
Sign In or Register to comment.