Well, openGL is not as pretty as the renderview images, so I kept looking, and found this awesome script:
https://github.com/ArthurYidi/Houdini-Quick-IPR-Preview
Here are complete instructions, not long, but maybe not intuitive for everyone...
I put the two .py files in this directory, then restarted Houdini:
/opt/hfs16.0/houdini/python2.7libs
I imported the new modules in a Python shell in Houdini:
import tiff
import renderIPR
This script needs to know the name of your Render View. In the Python Shell I did this:
p = hou.ui.paneTabs()
print p
and then inspected the contents of p manually (well, with my eyes, so... visually?). In my case the Render View pane was p[3], like this: <hou.IPRViewer panetab3>.
Knowing the name of the Render View pane, I created an IPR object, as defined in the file renderIPR.py. I named it J:
J = renderIPR.IPR(p[3])
I set the frame range for a quick test:
J.setFrameRange(0,10,1)
The first time I tried:
J.render()
it failed saying invalid plane. It was looking for the color plane in the Render View, but I hadn't rendered anything yet. I rendered one frame with the "render" button in the UI, then tried:
J.render()
again, and it worked! It made a render directory and dumped 10 frames in there.
I hope this is helpful to anyone wanting to save out a render view frame sequence.