Interpolation

Interpolation is the calculation of intermediate values between defined points (keyframes or samples) to produce a smooth transition. In 3D it is used to compute positions, rotations, scales, morph targets and other animation parameters between keyframes; common methods include linear, spline and slerp (for rotations). In Audio/Video interpolation refers both to smooth parameter automation (like volume or panning) and video frame interpolation (frame blending, optical flow) as well as signal-processing techniques in sample-rate conversion or crossfades; here too linear and higher-order methods are used to reduce artifacts.

Imagine a 3D character with a keyframe at t=0 where the arm is raised and a keyframe at t=1 where the arm is lowered. Interpolation computes the intermediate positions and rotations (for example using a cubic-spline for position and slerp for joints) so the motion appears natural. In a video edit project you can use interpolation to go from 24 to 60 fps: the software generates intermediate frames using optical flow or frame blending so motion looks smoother. In audio you might apply interpolation to volume automation: between two volume keyframes intermediate values are calculated (linearly or with easing curves) to avoid audible jumps; similar interpolation math is used in sample-rate conversion to estimate new sample values without introducing artifacts.