Hitfilm Chopping arm off without going "though the arm"

I am trying to figure out how to cut an arm off with hitfilm.

I firstly want to try and make the effect work and chop off my own hand. Then later try to chop off a hand in a lightsaber battle. The problem is when recording I swing the lightsaber at the "top" of the arm. But what do i then do since I am not able to go through the arm? I have tried moving the sabre to the underside of the arm and do a jump cut. But that obviously didn't work. So my question is how would I record it. And how would I edit it? I have seen various youtube videos but those don't really showcase my use case

for example in this video

https://www.youtube.com/watch?v=n7SWEBX6HeE 

They don't show someone standing by and cutting the arm off with a blade or sword and so on.

I think i have seen some video with someone during the swing in front of a green screen and then adding it onto the footage. But that isn't really ideal for a lightsaber battle.

I hope you understand my Question :)

 

 

 

Comments

  • tddavis
    tddavis Posts: 5,202 Expert

    @danilkp1234 Sorry, away from home and can't do a video demo at the moment, but I'll try to outline my idea.  Shoot a clean plate of the room (or location) of the shot.  Hopefully it's just a quick static shot and the camera isn't handheld or moving. :)  Then refilm what you have done in the clip but let your arm fall away as the blade comes down.  Then without moving your body film a segment where you raise your up to reveal a "stump."  Use a mask to make the arm on the first clip disappear right when the blade intersects with it and you let it drop away for the blade to pass, then use the clean plate to replace it.  Create a duplicate layer and use the pen mask to isolate the arm you want to remove and export it as a PNG with transparent background and re import. Use this to make it fall off under the arm/blade clip but above the clean plate.  Do the same with the second clip and the clean plate by this time the arm would likely have fallen out of frame but if not add that PNG in as well between the layers. Use light wrap to blend the edges of the top layers to the clean plate layer.  I'm sure I bollocks that description horribly but I hope you can understand my rambing anyway. :) You can add burn marks and blood to a stump and import as a PNG but you will have to track the shot and create a point to attach it and that I can't do to save my life. Hope this helps a tiny bit at least.

  • @tddavis i have done the reshoot. Is this how you meant I should do it?

    https://drive.google.com/file/d/1fjdMTqdKdljB7G2hcPuKOh8kvbloc5E-/view?usp=sharing

    Then i should without moving my body raise my arm up then? find a stump on my arm?

     

  • tddavis
    tddavis Posts: 5,202 Expert
    edited March 2020

    @danilkp1234 You don't need to throw your arm back so hard, I think.  Here is a quick and dirty example of what I meant. Keep in mind, I don't have a lightsaber to use so only a broom :) and I am no where near as skinny or young as you are .  I tried to repeat it a few times and on the last I tried doing a slight jump cut (but all without masking) to illustrate.  Ideally choosing an angle where the arm doesn't cross in front of the person would be better but swinging by yourself makes that hard to stage.  You could even during the filming drop in a close up of the arm sequence showing the amputation then back to the arm raised to reveal the stump.

    Don't giggle and laugh too much: :)

    https://1drv.ms/v/s!AsoyBtMWsTrhgd83Su4dR2HTdR_VqQ?e=gSoZgl

  • @tddavis Thanks! now i know how to record it. I would record it like that an import then? would i try to mask out my hand on a duplicate of my footage and export it as a png sequence or something?

  • tddavis
    tddavis Posts: 5,202 Expert
    edited March 2020

    It doesn't necessarily need to be video footage.  Just mask the hand and wrist out and export as a PNG.  Itll be falling g off camera so quick and if it has motion blur added it'll be pretty believable... I think.

  • @tddavis i understand the part that i have to animate a png of the hand moving out of frame but how do i combine the arm and shut of the lightsaber swing

  • tddavis
    tddavis Posts: 5,202 Expert
    edited March 2020

    @danilkp1234 I am assuming you intend to replace the lightsaber blade with an effect of a glowing one and will use the stand in blade for tracking, yes?  Track the blade before you mask the arm out as this will also remove the blade where it is over the arm to get it's full motion of the downward swing.  Then mask the arm out not worrying about the blade at this time.  Use the clean plate to fill in where you masked out the arm and part of the blade then create a lightsword effect and use the tracking data to link it to the parts of the stand in blade still visible.  This will go on a top layer to cover over the masking.  Put the PNG of the "falling arm" under the blade layer effect but over the clean plate layer.  Keep in mind, I have never done this so there is liable to be some actual fiddling I haven't thought about involved, also, I cannot track to save my life, so you are probably far better than I. :)

  • danilkp1234
    danilkp1234 Posts: 78
    edited March 2020

    @tddavis Hmm

    now I have the saber tracked and the hand as a separate png but that do i with the hand moving out of the frame?

  • tddavis
    tddavis Posts: 5,202 Expert

    @danilkp1234 Mask out that arm just above the orange wrist strap and roto the mask to follow the arm.  The only place it will be a problem is if the arm is in front of you.  The clean plate will take care of the background that is deleted by the mask.

  • @tddavis so i would mask out the arm and roto it for the rest of the video even though i am moving the arm so it doesn't block the lightsaber?

  • tddavis
    tddavis Posts: 5,202 Expert

    @danilkp1234 Yes, so it looks like the hand has been cut off.

  • @tddavis the problem is the point with the where the saber would go though the arm the arm is already nearly out of frame. What can i do about that?

  • tddavis
    tddavis Posts: 5,202 Expert

    @danilkp1234 I don't think there would be any other way to fix that except reshoot it so the arm just drops down out the way to let the blade pass down and mask it out when the blade passes it.

  • @tddavis What I am trying to say is when the lightsaber would hit the arm is already out of the picture. If I needed to do a reshoot how would i then do it since i would have to move the arm to do the full lightsaber swing and then the arm would still not be in the right position for right at the moment where it would impact the arm. Since I needed to move the arm away according to lightsaber?

  • tddavis
    tddavis Posts: 5,202 Expert

    @danilkp1234 I was thinking of just dropping the arm so it stayed in frame but masked to a stump kind of like what I was trying in the awful clip I linked.

  • @tddavis i get the part with cutting the arm into a stump but i would need to change the time in some way to make the arm not be moved away almost out of frame when the saber is supposed to impact the arm in the screenshot above in the above post you can see the arm is almost out of frame at the moment the lightsaber should impact the arm

  • tddavis
    tddavis Posts: 5,202 Expert

    @danilkp1234 True, but I don't think you can change that with the current clip as is, or if so, it is definitely outside my knowledge.  I think the clip has to be reshot with those logistics in mind. Sorry, I can't be giving a better solution  but I am limited with Hitfilm knowledge.

  • FilmSensei
    FilmSensei Posts: 3,114 Expert

    @danilkp1234 After being asked to take a look at this thread, here is my suggestion...

    I would shoot the footage with a lightsaber prop where the blade is either shortened or removed. Then I would mask out the arm that is being chopped off and hand-animate it to either fly away or drop. Make sure you have a clean plate. Here is a super quick and dirty example of what I mean. This would be by no means a finished shot, but it gives you enough to get the jist of it...

    https://www.mediafire.com/file/gaj6wmbjszevh4c/Cut_Off_Arm.mp4/file

  • danilkp1234
    danilkp1234 Posts: 78
    edited March 2020

     @FilmSensei Okay. That could also be a way of during it but if you were to try and implement it in a lightsaber fight it would be hard to act without a prop blade but thanks for your answer :) 

    @tddavis Yes, I would probably need a reshoot. But what would I do differently in the reshoot? and as shown in the image below you can see the moment where it's supposed to go through the arm. the arm is already moving way out of frame. How would I fix that? a reshoot? and what would I do differently?

    Here the arm is supposed to be cut off but its already out of frame

     

  • FilmSensei
    FilmSensei Posts: 3,114 Expert

    @danilkp1234 I am not suggesting taking off the prop blade for the whole fight scene. Just take it off (or shorten it) for the one shot where the arm gets cut off. Keep the blade on the rest of the time. Check out this video I made a few years ago...

    The very first shot of the Sith (where he pulls out the saber and lights it) there is no blade prop. The second shot of the Sith (when he throws off the cloak) there is now a blade prop on the saber. Likewise, when the Jedi pulls out her saber, there is no blade prop on it initially, but then in the very next shot when the Sith attacks, they both have blade props attached. I hope that makes sense!

  • @FilmSensei yes but if I take the prop off for one shot then I would have no reference for where the tip of the blade should be. is it possible to just make the tip point the hilt point offset by y value? that is the only way i could i see the blade length to  be constant through the whole saber swing