Water/liquid/air flow animation in Bongo

Hi everyone!

I just started with Bongo and I wonder if any of you experienced people know how to create a simple animation of water/liquid/light/or air flowing through the pipe?? Liquid moving through the pipe with arrows suggesting direction of the flow would be absolutely amazing!

A bit like this: https://www.youtube.com/watch?v=2nkAkJXKtIU (… or better! :slight_smile: )

Could this be done with maybe path constraint somehow? Any help would be massively appreciated!


Bongo 2 is not designed to do water simulations, but simple ones can be “faked”.
Like water rising in a pipe like this:

All you need to do is to make a line, activate Record History and add a pipe to the line.
Then just animate the line stretch and the pipe (as in the water) will follow.
Example model can be found here Water_in_pipe_B2.3dm (138.7 KB)

Please note: If you press play on the timeline you’ll only see line move, the viewport won’t keep up with the animation in real time. Rhino - Display Problems

Hi Marika

You’re a genius! This is perfect! Thank you so much for taking the time to reply! Xx

Ps. I like the idea of controlling the action with the line/curve, do you reckon there is a way of having that ‘liquid’ go around the bend of the pipe?

I did some experiments, using a curve with lots of points which I then moved manually one by one along another hidden and locked curve. It sorts of what I wanted, but it’s a bit of laborious process and it doesn’t look very smooth:

I will speed it up in video editing software which will probably make it look a little bit better, but do you have any ideas how to do it differently (more quickly and easily)?

The use of Rhino’s Sweep1 and Bongo’s Look Along Simple Constraint is an alternative.
BlackMamba535.3dm (177.2 KB)
The centerline is equipped with 2 disks (the diameter of the liquid). One is made traveling along the curve by applying a ‘Look Along Curve Normal’ Constraint.

Then, with Record History enabled, Sweep1 is executed using the edge of both disks as ‘sections’.


PS The video http://bongo.rhino3d.com/video/the-power-of-history shows more History based techniques.

Hi Luc
Thank you for taking the time to look into that. I’m sorry but I don’t know how to execute your example?

  1. I created a circle and curve first:

  2. I click animate → select keyframe → select my circle → and when I add simple constraint, rhino is asking me to pick vector? When do I sweep?

And will I be able to apply colour to that ‘liquid’ moving with sweep?

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Good morning Luc,

Apologies for not replying any sooner. Thank you so much for creating the video with a fix! I always find videos easier to follow and seeing where you change that parameter to 0.001 really helped. What a fabulous support service you and Marika provide! Worked like a treat, thanks one more time.

One last question, if I may:
I rendered an animation test (avi), selecting frames from 25 to 50 (ie where it goes on the corner), but for some reason the output BMP file for 50th frame, doesn’t look like 50th frame on my screen? Have I done something wrong? Is it because I increased ‘length in seconds’ option?

Are you able to share the model so we can have a look?

I just did a quick test and didn’t save the model, but it’s ok, I was just curious about those settings but it’s not very important, moving liquid was the main thing! thanks

Take a look at this topic. It deals with the relation/difference between Ticks and Frames

In short: In the Render dialog…

  • the top section “Input” of handles the range of ticks you want to render.
  • the bottom section allows to make a selection out of the frames to render, as defined in the middle section. Generally the option ‘Active time segment’ is appropriate . It’s because you entered 0 to 50 here that you only got 50 frames, and hence a movie of only 1.66 seconds instead of 8.

I agree it’s a bit confusing. I hope we can improve the user interface in Bongo 3.