Okay so basically I have a model of an engine. enter image description here

The purple shows where all the gas and yes gas not liquid should go. It must collide and be held in by a couple moving parts. The first thing I tried was to use a particle system. The collision stuff was waaaay too bouncy so I tried to use a follow curve forcefield. And after getting frustrated with that I tried using a smoke sim and smoke colliders and the air would not even go into the top. The inside and outside mesh are one in the same if that matters. And if so should I attempt to separate the two?

So I gave up and was going to manually edit a bunch of frames in GIMP but that was waaaay too much. So now I am here after many hours.

Would it be best to use a fluid sim and forcefields? Or is blender just not the software for that kind of thing?


1 Answer 1


Smoke seems like the correct medium to display airflow. Since Blenders smoke does not support suction, you'll have to fake the flow using multiple Forcefield.


  1. Model a simplified collider and mark it as a smoke collision object.
  2. Add an emitter which is fitted into the collider.
  3. Add a forcefield to direct the smoke.

If you use multiple forcefield, make sure they don't intersect by using the maximum distance and falloff properties.

In the smoke domain, decrease the temperature difference to a small value. Otherwise the smoke will drift upwards or downwards on its own.

smoke setting temperature

Hide the collision object before rendering.


Connected smoke interacts. This enables us to fake suction by filling the whole domain. I filled the whole domain with red smoke, except for the entrance. After the first frame, no red smoke is emitted (keyframe the Volume Emission), but green smoke is continuously being emitted. The green smoke will now get pulled even though it does not intersect with the forcefield.

connected colored smoke

With rgb colors, we can extract the color information and use it as a mask for rendering.

settings material

  • $\begingroup$ Wow, I had no idea things like this could be done in Blender. Thanks for your detailed answer. $\endgroup$ Dec 21, 2019 at 11:52
  • $\begingroup$ As previously stated thanks a bunch now would I be able to change the color of the smoke as it moves along to denote temperature? That was the initial reason for using particles. Thankfully I can do it by region so I might be able to put a texture on the volume material. $\endgroup$ Dec 22, 2019 at 1:55
  • $\begingroup$ Hi, I guess that's not to difficult as well. But it is an entirely different topic, worthy of a new answer. I suggest you thouroughly search blender.se and write up a new question with a simplified illustration if you don't find anything. Ping me here with a comment if you want. $\endgroup$
    – Leander
    Dec 22, 2019 at 7:52
  • $\begingroup$ I think I can figure that out however I hve an issue with my collision mesh. Does it have to be rather thick and have good geometry? Because current;y I am able to have the smoke collide with it on the outside but when I put my flow inside of it I still have the issue of the smoke not really moving anywhere. Edit: I think I misunderstood your post so the red smoke is being emitted by the colliders volume? $\endgroup$ Dec 22, 2019 at 20:24
  • $\begingroup$ Yes, use good, low-poly, manifold, watertight, thick geometry, like in the first image. The colored smoke is emitted from separate geometry (also good, low-poly...). The emitters and collider do not intersect. The red smoke is only emitted one the first frame. $\endgroup$
    – Leander
    Dec 22, 2019 at 20:32

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