the "Bypass" feature in imaging

[Kenneth Wang]

Hi Lisa et al.,

At the risk of expressing an unpopular opinion, I will say that I do
use the Bypass feature in imaging pipelines, and I do find it to be a
valuable capability.  While I agree that it is always possible at the
application level to reconfigure a pipeline, I will also argue that
there are situations when this is not necessarily a simple thing to
do.  In particular, in certain situations I find it useful to overlay
a functional interface on top of my vtk pipelines.  That is, I write
functions which hide the construction, configuration and modification
of vtk pipelines from the highest-level callers.  This greatly
simplifies matters at that highest level.  However, when that
functional interface entails pipelines which have branches dynamically
added or deleted, it's very useful to not require global knowledge of
the pipeline structure, though that's what we require when we talk
about an application re-connecting the pipeline.

On the other hand, I realize that maintaining the Bypass feature is
essentially just throwing a hot potato back to vtk developers, and I
believe it when people express the opinion that Bypass leads to
complication of pipeline execution management.  It's certainly
important to provide simple, robust execution semantics which are not
too difficult to implement correctly.

So, I just wanted to add my opinion to the discussion: Bypass can
definitely be very useful from an application-level standpoint, but I
realize that this doesn't necessarily mean it should stay.

-Ken




------------------------------------------------------------------------
Kenneth C. Wang			E-mail: kenwang at stanfordalumni.org
Electrical Engineering Dept.	Voice:  (650) 725-0458
Stanford University		Fax:    (650) 725-7731
CIS 214, Stanford, CA 94305	Web:    http://www.stanford.edu/~kenwang
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