“Beam Fractals” provided by Cullen Hassel


Is MOPs really free?

Yes. MOPs is free and open source (LGPL). It will stay open source. Don’t worry. MOPs Plus is a paid add-on to MOPs that includes new powerful tools that you can purchase here.

Does MOPs work with [operating system] [Houdini version] [Houdini license]?

MOPs is entirely Houdini SOPs, VEX, and Python. It will work with any operating system or Houdini license. The minimum Houdini version to run MOPs is 18.0, but you should consider using Houdini 19.0 at a minimum for compatibility with MOPs Plus.

Are MOPs a special kind of object in Houdini? Is MOPs a closed ecosystem?

No. MOPs operate on Houdini native packed primitives and geometry. With few exceptions, MOPs nodes will work on anything represented as points, whether they’re packed primitives, particles, or polygons. In most cases all you’d really need for stability is an “id” attribute on your points. You can mix and match MOPs nodes anywhere inside your SOP networks.

Will MOPs teach me how to use Houdini?

Not if you’re a total beginner, but it will make transforming things much less painful. MOPs still largely relies on basic Houdini workflows like attributes and groups. As long as you’re comfortable manipulating those, you should be fine with MOPs.

If you’re an intermediate or advanced user (nerd), you can of course open up the HDAs and peek around. You could learn something new, or even better, find a better solution and submit a pull request on Github!

How do I install MOPs? Do I have to edit some ENV file…?

Check the README on Github for the most up-to-date installation instructions. If you’re using Houdini 17.5+, installation using the “packages” method couldn’t be easier… you don’t need to edit the environment at all.

How can I contribute?

Aren’t you generous! There’s a few ways you can help out MOPs:


The best way to learn is to take a look at the MOPs Wiki, and look at the /examples/ HIP files that are included in the download. Or just ask in the forums!

There’s also a MOPs Discord server with lots of experienced and new users alike: MOPs Discord

For more documentation options and tutorials, check out the Documentation page.

MOPs Plus

What does MOPs Plus offer that MOPs doesn’t?

MOPs Plus contains a bunch of new SOPs for things like Typography, blending cameras, building velocity fields, assigning textures based on simple attributes, and many more tools for creating motion. It also contains MOPs DOPs, a suite of dynamics solvers for easily directing simulations.

To see exactly what nodes are new, check out the MOPs Wiki node list and look for nodes marked “Plus”.

How much is MOPs Plus?

MOPs+ FX (.hda) is $220 a year. MOPs+ Indie (.hdalc) is $100 a year. If you’re using an Indie license of Houdini, get MOPs+ Indie. You can always upgrade for the prorated cost difference.

Wait, MOPs Plus is a subscription? I hate those.

MOPs Plus is different from typical SaaS models. When you buy a license of MOPs Plus, it is yours to keep, permanently. The subscription you buy from the site can be paused at any time, and you won’t be charged again. Maintaining an active subscription entitles you to download newer versions of the software, up until the expiration date of your latest subscription (1 year from the last renewal). If you don’t want updates, you can just leave the subscription paused (or cancel) and you won’t be charged again.

What versions of Houdini is MOPs Plus compatible with?

MOPs Plus will work with Houdini 19.0 and newer. There are separate installations depending on your Houdini’s Python version (3.7, 3.9 or 3.10). Please make sure that you download a build of MOPs Plus with the same Python version as your installation of Houdini! Otherwise you’ll see strange errors on most nodes when they cook.

I have an active subscription but I’m getting an error saying this version of MOPs Plus is newer than my subscription allows. What’s going on?

You just need to activate the license again. This is required anytime you renew your subscription, so that your license file is regenerated.

Header image provided by Maxime Hacquard.