The human eye is remarkably sensitive to movements that don't look right, so if the transition speed doesn't match the movement of the slider, it will look wonky. I would guess that the slider has a speed curve, with an acceleration and deceleration to avoid hard stops and starts, which you will also need to match if you don't want things to look wonky.

Generally speaking, for dynamic background replacement like you have in mind, you would need some kind of motion tracking system sending data to graphics software which renders the background in real time.
For example, some PTZ cameras emit tracking data so that a virtual camera in the graphics software can replicate the PTZ values, rendering out the background from the point-of-view of the real camera. Unity and Unreal are often used for 3D virtual sets, as well as TouchDesigner and Notch, as they can render out the background in real-time and send the image to the video-switcher as a background for the keyed camera shot.

Having said all that, if your background is a 2D image which could be repositioned to match the motion of the slider, it might be worth trying a simpler approach...

You might want to look into whether the slider controller can send out tracking values, with real-time data about the position of the slider. If so, a software package like TouchDesigner or Chataigne, that can read in values from one system, remap the values to another range and send them as commands to vMix, might allow you to move the background layer in response to the slider position. For example, the vMix web API has a 'SetPanX' command, which could move the position of a background image. The SetPanX command takes a value between -2 (full left) and 2 (full right), while the slider might send out values between 0 and 65535 (or some other range of values), hence the need for some 'translation' by other software in-between.

How about pre-producing the background move. Then when you switch to the slide cam you trigger the background movie as well. Or but them into layers.
Another option is using a virtual set in vMix. You can set the speed to custom matching the slide duration.

Professionally one would use a cam tracker like Stype and use that data to live render a 3D scene on LED background. A good demo is from last IBC

Okay, thank you so much for the ideas, Yeah we have tried out some stuff with the virtual studio, and thats kind of the way we thought to go.
Stype looks very interesting, i am going to take a look at that!

I am curious to know how much “untracked” camera movement you can get away with.
Software like Vset 3D and Wasp3D show samples of stationary cameras used in 3D sets which look pretty convincing, so a lot will depend on the parallax movement and angle changes in relation to the camera’s footprint on the background.
I am guessing a smaller subject (standing talent) on a large set is less “disruptive” to the human brain than a larger footprint item (like a desk and/or medium shot or CU of talent) which will require “coordinated” or tracked camera movements.


Ice