First of all, thanks very much to everyone who answered, that's what I love about this forum.
Special thanks to @Woland for your long and specific answer.
I've been doing some testing on these things, I post what I found in case somebody else finds it useful:
- The error in 2.6.1 was indeed caused by my 3D models, but not by the file itself, rather than the path. For some reason, if I put the 3D files in my desktop, Isadora has no trouble, but whenever the files are inside any folder, the error window pops up.
- The mouse watcher error only happens with an imported 2.6.1 patch. The mouse watcher works as expected in Izzy 3 if you make a new patch, but it doesn't if you open an old file. Maybe if I was able to save it (updating it in the process) it would behave correctly afterwards, but I have no way of knowing this... yet.
- As for the Blur taking up a lot of CPU usage, I found out that a missing FreeFrame plugin could be the actual problem. After I installed the FFMotionBlur (which was in the 32-bit plugins folder but not in the 64-bit one) the scene runs in Izzy 3 more or less the same way than in Izzy 2.
Thanks again everybody. I think I will be updating to Isadora 3 very soon, since it's clearer now than the problems were more closely related to using Izzy 2 in Mojave and I really want to try some of the new features (like Blind Mode and such). Cheers.
I would like to reformulate here a request than I made some time ago in an other thread: I am looking for other types of blurs than - or an enhanced version of - the standard Isadora's Motion blur.
Indeed, the current Motion blur, on some textures, makes 'spots', that is 'colour banding':
In Isadora 2.6, I was able to achieve something more satisfying with Trails, which unfortunately cannot work in Isadora 3.
It is possible to avoid such color banding in Max/Jitter just by forcing textures from 'char' to 'float32'.
I presume it would be possible to adapt Isadora's Motion Blur code to do something similar in GLSL, is not it?
Let me precise that we have been several looking for all types of GPU blurs regularly and for a long time (actually years now) on places like ShaderToys and others, but could not find anything satisfying in terms of quality so far.
@AlexWilliams - or to build on @jhoepffner's scene - make your background a blur of the source as well - is that what you meant? the 'blur gradient' is affected by the amount of blur on the shape, and the background blur is the maximum outside.