Fluid animation and obstructions...


I have been following some of the tutorials online and made the basic fluid animation of fluid moving moving from one point to another, but I have some questions regarding other functions.

If anybody can help with any idea’s where I might be going wrong I would appreciate it.

  1. I have tried to place obstructions in place of the flow but it seems to completely miss it, passing straight through it.
    Do Obstruction objects all have to be within the Domain?
    Why can I not seem to use a Cylinder or other shape as an obstruction?

  2. I cannot seem to get a constant flow using Inflow and Outflow. The inflow works fine but the Outflow does not.
    Again, does the outflow mesh have to be inside or outside of the domain?
    Does the shape have to be the same as the inflow?


  1. Obstacles have to have fluid simulation turned on and be set to “Obstacle”. Depending on the mesh, you should do either Init Volume, Init Shell, or Init Both (try Init Both if you’re not sure which to use). They don’t have to be in the domain the whole time, but obviously the fluid is always in the domain, so in order to interact with the fluid they have to be in the domain. They can be animated to pass through the domain though, and they will have an effect.

  2. Outflow doesn’t give you a “flow” exactly. It eliminates fluid geometry that it touches. So it will remove fluid from your domain. You can use it like a drain, or to absorb splash, or other ways. It only affects fluid that touches it, though, which means that it must at least overlap with the domain or it won’t have any effect.

Thanks for the reply.

In messing about with fluids, what I was trying to achieve was a constant flow of water running along a narrow channel, and in order to keep the level constant needed the outflow to match the inflow.

I just cant seem to get the outflow to work.

Dont suppose you could post up a simple blend (something like a cube) with outflow working so I could see what I was doing wrong?

I guess you have seen this tutorial…?


Here’s an example. The shape and size of the outflow doesn’t matter. Probably you need to adjust the inflow velocity on the Inflow object. Also, like with real fluid, it may take a little time to stabilize. Imagine pouring water through a real tube that’s open on the far end. If the water isn’t totally rushing through the tube, it’s inevitably going to taper off at the end.


May I suggest watching LOTR Junkie’s video tutorial in the tutorial section? Its quite useful.

:)Thanks for the replies

Yes I had but it doesn’t deal with the Outflow issue for which im struggling to get to work.

Thankyou very much for taking the time to give me a blend to look at, very much appreciated:)

Thanks, I hadn’t seen that, but will do a search for it now.

There are some really good tutorials in this thread.

They cover pretty much everything fluid related.

Thanks very much fatfinger :slight_smile: