Weekly Development Notes #11 – Safely updating the FLIP Fluids addon and fluids that buckle, fold, and coil

Covering the week of March 2nd – 6th, 2020.

Hey everyone, it’s Ryan here with our 11th weekly development update of the FLIP Fluids addon for Blender! Last week on Wednesday we released version 1.0.8 of the FLIP Fluids addon which fixed many bugs and usability issues.

We had a bit of bad luck with this release. Last week we found out our Apple hardware used for generating macOS compatible builds died over the weekend. Luckily we were able to quickly get a new Apple system and after setting it up with our development environment, release was only delayed by 2 days. The week before, we had to fix our Linux system that was stuck in a boot loop, but this ended up not being too difficult to fix.

This development update will be a bit shorter than usual. We’re receiving a large volume of support requests and questions and I’ll be working through them all by the end of the day. This is quite normal after a new FLIP Fluids release where we send out a mass email to our users. The last version release was in November 2019, and for hundreds of our new users since then (including a lot of new Blender users!), this will be the first their time updating the addon.

The safest way to update the FLIP Fluids addon

According to our Addon Installation and Uninstallation Guide, the safest way to update the FLIP Fluids addon is to:

  1. Restart Blender
  2. Uninstall previous version
  3. Restart Blender
  4. Install new version
  5. Restart Blender

The reason for all of the restarts is to ensure all older installation files are removed correctly, older scripts are unloaded from Blender, and files are not in use during installation. The final restart is required to run scripts that are only triggered when Blender is re-opened. These scripts complete the installation and handle updating any compatibility differences between the old version and new version.

Following the above steps are a ‘foolproof’ way to update the addon and eliminate potential errors that can occur in rare cases. In most installs, you can probably get away with following just steps #4 and #5, but with thousands of installs, even if there is just a small chance of something going wrong, it is inevitable that a few users will encounter an issue related to an installation error. For this reason, it is recommended to always follow the above instructions exactly.

Slime Noodles

A very cool, and very weird high viscosity experiment by Dennis. Rendered using EEVEE in about 20 seconds per frame!

I sometimes see comments online where someone has seen our high viscosity simulations that buckle, fold and coil, but they can’t seem to achieve this in the built-in Blender Elbeem or Mantaflow simulators. If you have tried doing this with the built-in Blender tools, you may have found that instead of fluid buckling and folding over itself, the fluid just clumps into a pile of jelly.

The reason for this is that out fluid engine use an accurate viscosity solving method that takes into account shear stress at the liquid surface. This is what makes it possible to simulate liquids that buckle, fold, and coil. The built-in Blender tools use a more basic viscosity method that is not capable of these types of high viscosity effects.

The specific viscosity method we use is this one: Accurate Viscous Free Surfaces for Buckling, Coiling, and Rotating Liquids.

More Development Notes

  • Fixed bug that would cause materials on whitewater foam/bubble/spray objects to be removed after a render completes – This was a serious issue and I do not know how I missed this during testing. This issue affects the v1.0.8 02-mar-2020 version of the addon. We added a quick hotfix shortly after release to patch this issue. The latest version with the fix is v1.0.8a 05-mar-2020. If you have updated after receiving our Blender Market email, the version already includes this fix. Apologies for the inconvenience!
  • Fixed bug where particle draw size setting does not update the drawn particle size in the viewport – This is part of the particle debugging feature in the FLIP Fluid Debug panel. The release notes for v1.0.8 mentioned that this was fixed, but due to an error merging this feature branch into the release branch, this fix was not actually included in v1.0.8. This fix will be included in the next version.
  • Updated Documentation: Addon Installation and Uninstallation – Updated installation guide to use Blender 2.8 screenshots rather than 2.79. Blender 2.79 specific instructions can be found here.