Good day/evening/afternoon/night,
Right to the problem: I’ve been using Sequencer to set up scenes and capture 360 movies for a while and everything worked smoothly… until today.
What actually works
- Frames are captured
- Sequencer is executing
- Camera is moving (though it’s not rotating following the camera rig rail’s tangent)
The problem
Though the capture is actually working, there is a little positioning delay that causes the Capture component to “fall back” compared to other elements in the scene. Being specific, the POV is in a cart going through a rail but frame by frame, the cart is going back and forth as if the component took more than necessary to render a frame and Sequencer went ahead and ticked one more time.
Sometimes, the player hops closer to its position, but it really seems as if there’s a problem with the fixed time step not being respected 100% by the sequencer.
Base test
I tried to do this in a new level, starting from scratch:
- Create a new level
- Create a new sequence
- Create a new Camera RigRail
- Edit the spline a little (an “U” turn, for example)
- Create a Camera Actor and place it in the level
- Create a simple Cube
- Attach the cube to the Camera, so it moves with it
- Add the camera to the sequence, setting the track as the RigRail previously created
- Configure the stereo capturing (fixed rate, “SP.” commands, blueprint to begin the capture)
- Capture the scene, watch as the cube “seems” to start to slip from it’s relative position frame by frame
Other attempts
- Attaching the cart to the camera component directly
- Using two rails, one for the camera, one for the cart
- Reducing Polys with extreme prejudice
What’s next?
I’m running some additional tests, like trying with a brand new project, but since I’m working in 4.15 rolling back is not an option.
¿Did anyone have this issue as well? ¿Is it related to sequencer and its frame handling?
Update!
Something unexpected happened. I was suspicious as to how did sequencer handle and calculate the different transforms per frame, so I made a little blueprint that printed some stats to be used as input. Turns out that the camera and the model, even when attached to one another, are NOT following the rail at the same steps like they should be.
The camera lags behind little by little, ranging from 0.1 to 1.1 units per frame both in the X and Y axis. Since there are no variations in the Z axis, no issues there. I’ll try adjusting the cart frame by frame to follow the camera with the delta between the two updates and see how I fare.