[yt-users] transparency and color from two arrays (cont.)

[Matěj Týč]

Hello guys,
our research group would like to visualize volume data, where the
transfer function is bivariate (see
http://lists.spacepope.org/pipermail/yt-users-spacepope.org/2017-April/008552.html
). We have been struggling with this task, so I would like you to help
me understand some of the basic concepts I have come across and that I
find confusing.

1. I think that I somehow understand the concept of transfer functions
with multiple fields, but I have difficulties of creating a volume
source with multiple fields. I have somehow examined the source code,
and it seems to me that only the first field is used (judging by
https://github.com/yt-project/yt/blob/master/yt/visualization/volume_rendering/render_source.py#L516
). If I am wrong and it is meaningful and possible to construct a source
with multiple fields, could you please provide an example?

2. I have no doubts that transfer functions work, but I was unable to
find out how are they involved in the integration process. What I came
across were the integration routines and they have mentioned that the
transfer function is not used:
https://github.com/yt-project/yt/blob/master/yt/utilities/lib/ray_integrators.pyx#L235
. This is really interesting, how is it in reality?

3. You have mentioned the PlanckTransferFunction as a good example of
multivariate transfer function.
However, doing a Google search, hoping that we will find a code snippet
featuring a non-trivial example did not yield any results. Would you be
so kind and provide one?

Best regards,
Matej

https://github.com/matejak