Scene recreation question: Camera tracking along sword from tip to hilt

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  02 February 2018
Scene recreation question: Camera tracking along sword from tip to hilt

Hi there!

I have a ten second long shot taken by a video camera. A sword is partially in view of the camera, with its tip being prominent. The camera tracks along the sword for about ten seconds until it reaches its hilt. Only about 20% of the sword is on camera at any given time.

The goal:
Add particle effects to the sword on camera. I think that I'd have tocreate a rough model of the sword that follows the sword on video.

Some notes:
* The camera is moving
* The sword is slightly moving (it is being held by a person)
* I have solved the camera in Cinema 4D and have many motion tracked points along the sword in Cinema 4D

The challenge:
I know how to track the sword if the entirety of the sword was in view of the camera. I do not know how to handle this when the camera is tracking along a portion of the sword when both the sword and camera are in motion.

I think that I don't conceptually know the process of how to tackle this challenge. I'm sure the workflow would transition to a myriad of similar challenges, such as creating a mask in After Effects of the moving sword that is being tracked.

My hypothesis is that I should take photos of the entire sword, model it, and then bring that model in to this scene. Then I would somehow pair that model with multiple sets of objects being tracked (via the motion and object tracker).



As a side note, I have the book "The Art and Science of Digital Compositing" by Ron Brinkmann. Does any chapter in this book explain the conceptual process of tackling this challenge?
  02 February 2018
Have you had a look at the Syntheyes tutorials? They're obviously made for Syntheyes, but often the concepts are transferable.
This one in particular may have some insights -
  02 February 2018
If you can get a 3d track of the position and orientation of the handle of the sword you should be good to go. Just parent your effects from that...and extend out to the tip or beyond.

Can you track a point at the base of the sword as well as a consistent point further up? If so you've got the vector that you need.
C4D R19 Studio, MODO 902, VRAY, Octane, Cycles. PC/Mac.

Last edited by IceCaveMan : 02 February 2018 at 02:26 AM.
  02 February 2018
I propose you manually track 2 points on the sword, and then use the "Motion Tracker User Tracks" XPRESSO node, to create 2 nulls.
Then Download the file I posted here:
and make a sword stand-in move between the Nulls.

If you want only particles, then you should be ok using this technique.

All steps required are in this thread:
Follow me on Twitter@nosemangr - Watch me on Noseman's Youtube Channel
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