Pose parameters for neck

[bing-jian]

"RingNet outputs a subset of the FLAME parameters. These parameters are the first 100 shape parameters, first 50 expression parameters, and the pose parameters for the global rotation (FLAME pose parameters 1-3) and the jaw rotation (FLAME pose parameters 7-9). "

Originally posted by @TimoBolkart in #7 (comment)

Wondering what are the FLAME pose parameters 4-6. Are these for the neck which is also a joint in the FLAME model? Does RingNet outputs pose parameters for neck?

Thanks,
Bing

[bing-jian]

Found the answer in the Ringnet paper Section 3.5 Implementation details:
The neck and eyeball rotations of FLAME are not regressed since
the facial landmarks do not impose any constraints on the neck.

The regression network consists of two fully-connected layers of
dimension 512 with ReLu activation and dropout, followed
by a final linear fully-connected layer with 159-dimensional
output. To this 159-dimensional output vector we concatenate
the camera, pose, shape, and expression parameters.
The first three elements represent scale and 2D image translation.

The following 6 elements are the global rotation and
jaw rotation, each in axis-angle representation. The neck
and eyeball rotations of FLAME are not regressed since
the facial landmarks do not impose any constraints on the
neck. The next 100 elements are the shape parameters, followed
by 50 expression parameters of FLAME.