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  • Writer's pictureEmi

VFX - Planar tracking

Updated: Nov 29, 2020

I've actually already done a planar track task during my first year of the NextGen course.


However, I lost access to my license before I was able to blog about the process so didn't get any of it down other than an image of my node graph and the rendered video.

It's in slow motion unfortunately, and i'm not sure how it happened. Other than that, the rat blends in rather nice but could have done with a little blurring.

 

In order to challenge myself and help jog my memory of the process, I've decided to revisit this task with a different video scan and also a different image to track on.

I chose to use a clip I found on the website Pexels that shows a walk through a street in Tokyo. The reason I chose this clip is cause I want to try placing a piece of art I made into the scene.


A slap comp is when an image is planted into a comp without being edited to fit in.

I've managed to get the asset tracked onto a wall, however people walking in front are making the track follow them. I've tried to put some work into making it so they don't affect it, but unfortunately I haven't succeeded yet.

This is what my Node Graph looks like currently:

The original clip had to be removed because it kept causing errors in nuke, instead I just kept the TGA file version.


For the images, I've used premult to make the transparency work. I did run into some problems which meant premult didn't work so instead I turned on auto alpha on the read-in images.

 

Process:

  • Import the camera plate into the node graph

  • Reformat to 1920x1080

  • Write the file out to your scans folder, with ####.tga at the end of the file name

  • Click render

  • Backdrops to organise the node graph

  • Turn on full frame preview

  • Read tga back in

 
  • Roto


  • Cusp Bezier


  • Remember reference frame

  • Make sure PT is on

  • Track forward and back

  • Correct Plane

  • Make sure you are on the key frame

  • Line up the correct plane with the track points

  • Don't move the correct plane when not on the key frame

  • Grid can help check perspective

  • need to export the track

 
  • Get a checkerboard to check the track

  • Corner pin 2D (absolute)

  • Merge camera plate and planar track export

 
  • Load in rat in place of the checker board

  • Transform

  • Luminance key with keyer

  • change the channel to alpha

  • Black is transparent, white is solid. mess with the sliders until the rat looks solid black and then invert the colours

  • Channel merge

  • Premult

 
  • Roto

  • Bspline around the graffiti


  • Make sure you are as close as possible to the rat

  • Merge the roto over the premult with (in) operation

  • Grunge

  • Merge the grunge using stencil to cut out a pattern in the graffiti

  • Blur

  • Write out as a mov file with apple prores 422 as the codec

 

Finished Node Graph:


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