1. original plate
2. remove lens distortion (undistort plate)*
3. camera tracking/matchmove
4. cg pipeline (undistorted)
5. render cg with overscan (undistorted)**
6. distort cg render
7. composite over original plate

* Step 2 assumes a lens distortion grid was photographed or lens mapping data was acquired. Step 2 is often part of step 3. Camera tracking software can calculate lens distortion from most plates.

** Step 5 is required when undistorting barrel distortion. If overscan is not rendered the edges of the frame will be cropped when distortion is applied.

Wikipedia: Distortion (Optics)
SynthEyes Lens Distortion Tutorials
SynthEyes Lens Distortion White Paper
SynthEyes Lens Distortion and Anamorphic Padding White Paper
3D Equalizer: Lens Distortion Model
3D Equalizer: Lens Distortion in 3DE4
3DEqualizer4 R4 [advanced] – Lens Distortion Pipeline / Export Distortion Data to Nuke