FBX camera import from a provided camera track, Getting it into position

Flame Flame Questions
1

Interested to hear you camera import tips.
Import .fbx
then play hide and seek for the correct axis
then muscle an axis scale, rotate, position to get it to line up.
The Flame camera tracker failed on these shots.
Looking forward to hearing your advice and tips.
Old dog looking to learn new tricks.
Thanks in advance!

2

Hi there! So I order FBX tracks from an Indian Vendor called CGLab on a fairly regular basis. I don’t know much about CG integration, but I do a lot of sky replacements and paint tweaks involving projection.

Usually I’ll make notes or diagrams of what geometry I’d like defined in their tracks. Then I import the FBX, and all I need to do from there is go into the action output menu and set the Camera to be the one included with said FBX. The ground plane and such come pre-defined.

To create projections, I duplicate the original camera and re-parent it to the same base axis. Then I alt click on all the position/rotation parameters on the frame I want to project on, it remains motionless. Then finally I parent a projector to that camera. Good to remember that projectors default to 500 as their Z value, so you’ll wanna set it back to zero.

I was never a professional matchmover, but I’ve dabbled in PFtrack and was able to get passable results using it, prepping FBXes and importing using the same method. That said India vendors have spoiled me - Sometimes I’ll even order 4 point 2d .stablilizer tracks from these guys as well if a screen replacement is looking especially fraught.

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3

I’ll add that if when importing the FBX you don’t see any animation, you may need to slip the animation in the FBX back by 1000 frames.

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4

you should not have to do this with an FBX camera and geo. Something is wrong if you have to do this.

You should load in the fbx, then set the camera output to the FBX camera (they usually come in named “Camera1”) and all the geo should be lined up. As Britt said, you may need to slip the keyframes in the camera by 1000f depending on how the track was done, but any more adjustments than that and something is wrong.

I’ve seen situations with a tracked camera and an OBJ where the world scales are off, but that’s just looking through the tracked camera and scaling either the camera or the OBJ to line up. No XYZ positioning.

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5

Agree w the other folks.
Animation timing offset and scale should be the only variables.

6

maybe I have a resolution issue.
So the chasing down an axis in the correct space is not needed,
Is their a video or document that shows this workflow.
Thanks for the tips.

7

I can’t think of a video offhand, but here are the steps I do:

  1. Plug backplate into Action
  2. Drag the Import node in and pick my FBX file
  3. Repeat to load Geo if it’s a separate file
  4. Select the imported camera and toggle the render can drop down to designate it as the render cam.

At this point if your Geo is not lined up the first thing to check is the keyframes. Flame defaults to 1. Some software and some shops like to start on 1001, so check the channel editor and slide the key frames back into place.

If things are STILL not lined up there is probably an upstream issue, but for due diligence throw a zeroed out axis in the scene and make all the Geo a child of it. Slide the scale around on a single frame to see if the Geo lines up when scaled.

Failing that, I get on the phone to whoever gave me the track and tell them it’s not working.

8

Hi Jeff-

this all seems covered above,
but for sake of clarity try this:

Start by confirming
you were given:
- fbx claiming to contain camera solve
- the plate used to track it.
- the stMaps generated for distort/undistort from camera solve.

Action node:

  • import the fbx to action schematic.
  • scale is important. autoscale OFF. It’ll be a factor of 10. Try 100, 10, 0.1, 0.01, etc
  • Scale varies by software. Houdini is meters, Maya/Unreal centimeters, and Flame seemed to match at mm.
  • Similar to frame caches, it’s worth noting fbx import can be either a true import or read from file on disk. Each has its advantages.
  • Action schematic should now contain camera and perhaps a bunch of addtl locators as axis.

Undistort plate w stMap then plug source plate into Action back.

  • The resolution doesn’t matter.
  • Sensor size is used to generate the camera solve.
  • the exported fbx won’t require the info, it’s baked in.
  • change output camera from default to the cam from imported fbx.
  • result should now be an action schematic full of locators w you plate as back.

Scrub thru and verify.

Likely to be a bunch of frozen pointers since frame offset is usually 1000

  • Select camera and go to animation panel w Shift+Tab to frame it.
  • Change the animation view option from “channels” to “tracks”
  • May need to hit shift+tab again to frame.
  • Plate exports are commonly exported starting at 1001.
  • If batch is set to default frame 1 as first frame, then offset the animation in x by -1000

Now should have lined up.
Confirm by scrubbing thru.

Hope that helps.

Andy D.

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9

Also this quick trick I’ve shared previously can be helpful with dealing w locators in fbx camera imports:

https://vimeo.com/manage/videos/455098298

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10

Thank you all. I was the victim of a bad track. The other camera tracks I imported yesterday worked great.

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11

Great news! I think we’ve all been there. It’s disorienting.