What exactly is an Interpolation Modifier? Well, to be honest, it's just a fancy way of saying how much you smooth (or interpolate) the input feeding the camera. A big drawback to simple virtual cameras (like a debug camera, for instance), is the fact that the input you give is translated 1:1 by the engine. Given that digital signals are either 1's or 0's, on or off, it inherently produces a very artificial feel.
But real cameras don't behave this way - they're heavy, they have inertia, and they're relatively smooth. They may have a camera shake or sway, but they're not jittery. You place a camera on a Dolly track, and the camera operator smoothly pans and tilts the camera to track a character through the scene. And in a way, an audience's brain is expecting this very same behavior when viewing a trailer or a movie - if we don't meet that expectation, their brain tells them something is off; That something doesn't feel right.
So to get around this, we can choose to give our virtual camera weight and believability. We do this through interpolation; and controlling just how much of it there is. The end result is something that's much more pleasant and believable to look at.
Use the slider to move from low interpolation (left) to high interpolation (right).
The lower the interpolation amount, the more raw your input will be and the less smooth it will feel. The higher the interpolation amount, the less raw your input will be and the smoother it'll feel.
There are no controller keybinds for changing Interpolation Modifiers on the fly. You can only change the amount inside the ImGui itself, as pictured above.
Not every shot has to be smoothed and heavily interpolated. In fact, high interpolation can often get in the way and make it impossible for you to track fast action scenes.
That being said, we recommend always thinking about incorporating some amount of interpolation, as even the slightest amount often improves how good a shot feels.