Faq

Frequently Asked Questions

As of January 2023

See the Official Marketplaces of the FLIP Fluids Addon page for where the FLIP Fluids addon is available for sale.
Or visit our Buy-page.

See the Official Marketplaces FAQ for how to download the FLIP Fluids addon product files.

Yes! All future version updates for the product are provided at no extra cost.

Before updating to a new version, you must first uninstall the previous version. In short, the safest way to update to a new version is to:

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

For detailed instructions on how to install or uninstall the addon, see: Addon Installation and Uninstallation.

Yes! Everything that you create with the addon is completely owned by you. There are no restrictions for what you can and cannot do with the content that you create.

The FLIP Fluids addon and content uses multiple licenses: GPL, MIT, and Standard Royalty Free. In general:

  • The Blender addon code is licensed under the¬†GPL.
  • The fluid engine is licensed under the¬†MIT license.
  • Some addon and product content will be using a¬†Standard Royalty Free¬†license. This license may cover content such as media (images/textures/videos), Blend files, materials, presets. Source code files will state their license at the top of the file. Assets will include a license file and information in their containing directory.

The FLIP Fluids addon and Mantaflow are both FLIP-based simulators. Mantaflow is the new fluid simulation system that was introduced into Blender 2.82. ‘FLIP’ is the name of a simulation technique that is popular for simulating fluids and is also found in many other professional liquid simulation tools.

Although Mantaflow and the FLIP Fluids addon both use the FLIP simulation technique, they are very different in what features are available, how features were implemented, and how the projects are developed. Mantaflow is a simulation tool for creating both liquid and gaseous/smoke simulation effects. Our FLIP Fluids project focuses strictly on liquid fluid simulation and we put a large development effort into reliability, stability, learning resources, and workflow features to help you create beautiful liquid simulation effects as quickly and as painlessly as possible.

Is the FLIP Fluids addon still relevant now that Mantaflow has been integrated into Blender?

The short answer is Yes! At the time of this writing, it has now been one year since Mantaflow has been added as the default fluid simulation system in Blender 2.82 (February 2020). Since then, our FLIP Fluids addon has continued to be a popular alternative to the Mantaflow simulator and has only grown in popularity.

Over the past year since it’s official release, Blender Mantaflow has come a long way in improvements, adding bug fixes and impressive new features. Our FLIP Fluids addon has also continued to improve and stay as a competitive alternative – and thanks to the amazing support from the Blender Community and funding via sales, we’re still able to keep up development on a daily basis.

Many of the aspects described in the topic below are still relevant reasons why our FLIP Fluids addon remains one of the¬†Blender Market’s best selling products¬†and a popular choice as a liquid simulation tool for Blender.

Update: The most recent weekly report from the Mantaflow maintainer was posted in September 2021 (view report here). According to a Blender developer, the Mantaflow fluid simulator currently has no active developer and current bugs will be marked as Known Issues (developer comment here | known issues here).

What are the benefits to your FLIP Fluids addon, compared to Blender’s new built in Mantaflow solver?

Paraphrased from this Twitter thread (February 15, 2020).

Most commonly mentioned by our users is that we are further developed for stability and usability compared to Mantaflow. It’s been over 2 years since we began the FLIP Fluids beta. I think a large contributor to our success was that we released a very polished product that was stable and just seemed to ‘work’.

Since release, funding through market sales has allowed us continue development full time for the last 20 months. It’s these thousands of hours of continued development that has furthered the usability, optimization, stability, and expanded features.

Usability: A large focus of our development is in usability and workflow features. Providing tools to help artists create simulation effects quickly and painlessly. Recently we have re-designed our product page to better highlight our usability features: https://blendermarket.com/products/flipfluids

Stability: Our fluid engine rarely ever crashes during simulation. Our beta testers really stressed our engine, putting it into situations we had never expected. Stability has been mentioned frequently as something that helps our users to run complex and long running simulations.

Customer Support: Another large focus for us is providing responsive support Monday – Friday. We have maintained a 5 star rating on the Blender Market and many reviews mention our helpful support. Communication with our users is very important for us to help improve our addon.

Documentation: Upon release, our documentation was a bit sparse. Over time, through support and feedback, we were able to better understand our users’ needs. Adding and improving on many topics, filling out our settings/UI docs with helpful notes and tips on common issues.

FLIP Fluids and Mantaflow are both simulation tools that use the FLIP sim method. There will be strengths/weaknesses for both software solutions. Mantaflow is a huge improvement for Blender’s fluidsim tools and is attracting many new users to Blender for simulation effects.

Mantaflow has only recently been officially released in Blender. There is room for improvement in usability and stability at the moment, but it’s great to know that the Blender Foundation is funding further development of the integration to improve and expand on the simulator.

Mantaflow is funded and developed by the Blender Foundation. The FLIP Fluids addon is developed by a small team independent of Blender and funded by sales though official marketplaces where the FLIP Fluids addon is sold. Thanks to the generous amount of support from the Blender community, we have been able to continue development and improve our product on a full-time basis since the initial release in May 2018!

For more information on how the FLIP Fluids addon is developed, see this comment.

Current bugs in Blender or stability issues in Blender can affect some features of the FLIP Fluids addon. Since these features are affected by an issue that is outside of our control, these features will be hidden by default. Enable the developer tools option in the FLIP Fluids preferences menu to unhide these features. The preferences menu can be opened with Help > FLIP Fluids > FLIP Fluids Preferences.

For the current issues, affected features, and workarounds, see the Preferences > Developer Tools documentation.

Is the FLIP Fluids addon right for your project? The FLIP Fluids addon is a liquid simulation tool based on the popular FLIP simulation method which is short for FLuid Implicit Particle. You should always choose the right tool for the job, and like a hammer, this addon might not always be the right tool to use.

There may be limitations in the FLIP Fluids development project, limitations in the FLIP simulation method, or limitations of Blender that may affect success in creating your desired fluid effect. See this documentation topic that details common limitations of the FLIP Fluids addon and Blender: Limitations of the FLIP Fluids addon.

Interaction between FLIP Fluids simulator and Blender’s rigid body simulator is limited. Rigid body objects can push around the fluid, but the fluid is not able to push around the rigid body objects. This is because simulation systems in Blender are run separately and do not communicate with each other. This limitation also includes interaction with Blender’s cloth and softbody simulation.

However, there are some convincing tricks that you can use to create the illusion of buoyancy where objects are floating around on your liquid surface. See this episode of our tutorial series for a detailed guide and example animations: Episode Seven: Buoyancy Tricks.

In general, the FLIP Fluids simulator and Blender simulation systems should not be used for scientific/engineering purposes where accuracy and validation is important. The simulator and simulation method is designed for use in computer graphics applications where complete accuracy is not needed and the fluid just needs to look plausible. Many shortcuts are taken during simulation in order to reduce processing time which also reduces simulation accuracy.

Some of the features/parameters in the simulator are not physically based, do not correspond to real-world physical values, and are just graphics tricks to help produce visually pleasing results. The simulator will not contain many of the parameters that you would find in a simulator aimed towards producing scientific/engineering simulations.

For simulation systems targeted for use in scientific and engineering, check out software packages such as OpenFOAM, SOLIDWORKS Flow Simulation, XFlow.

As of FLIP Fluids version 1.0.9 (26-nov-2020), a new force field feature set was introduced into the addon. See the Force Field Object Settings documentation for more info on our force field features.

However, there are some limitations to be aware about:

Can the built-in Blender force fields be added as a FLIP Fluid Force Field?

No, the built-in Blender force fields are not compatible with the FLIP Fluids addon. Our addon has limited access to Blender’s force field system and due to this, we are not able to use these force fields within the simulator. Our force field system is a separate and custom built physics system that is implemented directly within our simulation engine.

In addition to the limitations of Blender’s force field system, many of the force field modes we have implemented are for creating popular effects that are not possible using Blender’s internal force fields. Our force field modes differ from Blender’s in that they are specifically designed towards use in liquid physics and creating popular liquid effects.

Update: As of FLIP Fluids 1.5.0 (07-sep-2022), mixed/blended color attribute features and basic variable viscosity features have been added. However, these features are hidden by default due to a current bug in Blender that can cause frequent render crashes or incorrect renders when using these features. See the FLIP Fluids Preferences > Developer Tools documentation for affected features, a workaround to this bug, and how to enable these features.

At the moment, there is no support for multiple fluid simulation and mixing fluid materials in the FLIP Fluids simulator. The simulator is limited to a single fluid (and single viscosity) throughout the domain. Support for multiple fluid interaction is one of the most popular requests. We hope that we can add this in the future, but is not being actively worked on at the moment. This is a complex subject in fluid simulation and may require a significant amount of time for research and development, and some aspects of this feature may be outside of the scope of the FLIP Fluids project.

At the moment, multi-liquid simulation features only support color blending and variable viscosity. Features such as variable surface tension, variable density, volumetric liquid attributes, and separated liquid meshes are not implemented and some aspects of these features may be outside of the scope of the FLIP Fluids addon project.

Yes, it is normal for your CPU to run under 100% usage on average. CPU usage may be low on lower resolution simulations and is generally higher on high resolution simulations. Here are some explanations why the simulator is not running at 100% usage:

  • Fluid simulation is very memory heavy problem and memory access is slow compared to how fast your CPU is. In the simulator, there are many threads accessing large amounts of memory at the same time. The CPU threads must occasionally stop calculations and wait for data to be fetched from memory and this is what commonly causes decreased CPU usage in the simulator.
  • Some calculations in the simulator are not able to be multithreaded efficiently and must be run on a single core. These sections of calculations create a bottleneck which lowers average CPU usage.
  • The simulator may be running with too many threads enabled. It is possible that simulations could slow down from the overhead of running more threads than the simulator can handle efficiently. Some users with certain hardware (e.g. Xeon/Threadripper CPUs) may benefit from simulating with less threads enabled. You may experiment by changing the number of enabled threads in the¬†FLIP Fluid Advanced Settings. Try using half the number of threads and test whether you experience a speed-up in baking times.

Many simulations can be optimized for performance and detail by sizing the domain to tightly fit around your fluid effect. See this documentation topic: How large should I make my domain object?

The simulation calculations alternate between single threaded and multithreaded calculations. Single threaded calculation performance depends on high clock speed as well as high single threaded clock speed. Multithreaded performance depends on high clock speed and multiple cores.

A good all around processor for FLIP Fluids simulation baking would would have 4 – 12 cores (or 8 – 24 threads) with a high clock speed as well as a high boosted single threaded clock speed. High clock speed is the most important aspect of a CPU for this type of simulator in terms of performance. After around 12 cores, you will generally start see diminishing returns on performance when adding more cores.

For highly threaded CPUs (such as Xeon/Threadripper), these perform best for large simulations with a lot of fluid that spend greater than 1 minute per frame. For example, large simulations run on the Threadripper 1950X (32 threads) bake at over twice the speed of an i7-7700 (8 threads) in our benchmarks. These types of CPUs are very fast for the multithreaded calculations, but for the single threaded calculations, they don’t perform much quicker than any other CPU with the same clock speed.

Highly threaded CPUs are extremely fast for the multithreaded calculations, but for the single threaded calculations, they don’t perform much quicker than any other CPU with the same clock speed. They also perform very well for running multiple simulations simultaneously when splitting up the threads between simulations.

Whether you are caching your simulations on a hard drive (HDD) or a solid state drive (SSD) can affect how quickly your simulation runs. The simulator saves simulation files to your HDD or SSD at the end of each frame, and the CPU cannot continue calculations until the files are finished writing. Generally, file write speed on a HDD is much slower than on a SSD and for this reason it is recommended to cache to a SSD if possible.

For large simulations there will be more data to save to your HDD or SSD. The amount of data can often exceed 300 MB per frame. To test write performance for large files on your HDD vs SSD, you can try copying a 300 MB file. If your HDD is taking 5 seconds to copy this file vs 0.5 seconds on a SSD, this time difference can really add up over a large number of frames. 5 seconds spent on each frame for 500 frames adds up to over 40 minutes spent on just writing files!

The FLIP Fluids simulator is not GPU accelerated. As of addon version 1.0.4, GPU acceleration features using OpenCL have been removed and all GPU methods have been entirely replaced with higher performance CPU methods.

The simulation methods and techniques used in many of our features are not suitable for GPU processing. This is due to the nature of the types of calculations that our simulator runs. Many calculations of these features are not parallelizable enough to benefit from running on a GPU. Some features would benefit from being run on the GPU, however, switching between computations on the CPU and GPU can be slow and harm performance.

At the moment we do not have plans to add GPU acceleration features to the FLIP Fluids addon. We may visit this idea in a future development project separate from the FLIP Fluids addon.