It renders for me OK the first time, but if I toggle back and forth between rendered and lookdev modes it locks up in a memory allocation loop.

I suspect this is the same issue as in my https://developer.blender.org/T60379 which still needs some developer TLC (hint, hint, wink, wink, nudge, nudge).

Hi Gavin, your memory allocation loop sounds familiar. I have seen it in 2.79 also. It happens when I load either your disptest.blend or the test file above into yesterday's 2.80, but 2.80 does not crash.

2.79 does, with opensubdiv 3.3.3, and doesn't crash if compiled without osd support, or if Experimental features are disabled in the render settings, so no adaptive subdivision.

I can not reproduce this crash with my 2.79 build (with opensubdiv 3.3.3). And as you stated, I can not reproduce the crash either in 2.8.

@Sergey Sharybin (sergey) can you reproduce this on 2.79?

This does happen with own builds of blender2.7 and master branch, and with builds from buildbot.

As with my T60379 I presume that adaptive subdiv is complex in that the adaptive tessellation needs to be successfully recomputed basically whenever anything affecting the view or the subdiv modifier or the associated scene parameters change, and there are one or more issues with this, either dependency handling, or simply managing the reset of the adaptive tessellation stuff when things change and/or making sure that the computation has completed successfully before trying to do things based on that.

Thanks for the fix, Brecht. I completed a Blender RPM rebuild yesterday using all system libraries, so some versions differ from the Blender.org dailies. In particular I have LLVM 8.0 and OSL 1.11.0 but essentially my OSD version is still 3.3.3.

I can confirm that this fix cures my problem of the Blender crash when rendering in the viewport models using adaptive subdivision .

Richard