Occasionally, but not often enough I need undistorted plates for tracking, 3D and compositing. Because of this
I noted down this little workflow to help out my memory when it was again too long ago…
The undistorted grid. Using the ,LensDistortionâ€˜ node in NukeX with Grid Analysis.
This undistorted sequence gets cropped, ignoring that some pixels are cut off at all edges.Â toÂ 1920×1080 and
passed over to the 3D tracking software.
One workaround is to adjustÂ the horizontal and vertical aperture of the tracked camera and multipy it by a factor. For this
example I use the factor of 1.1. If your fov was 35mm, it now becomes 35/1.1=31.818181818mm.
Also increase the render size in the 3D application with the same factor. The new render size will be 2112×1188 pixels.
Applying again the lens distortion in Nuke will stretch the edges of the frame, but not in the important 1920×1080 area.
Then useÂ Â a 2D transformation after the distortion to match the frame center of the 1920×1080 and the 2112×1188 rendering.Â The center of the HD frame is atÂ 960×540. A transform of x= – 96 and y=- 54 pixels is needed when using a overscan factor of 10%.