I am doing this tutorial. I have this cylinder / lamp and an emitter plane (see arrow).

enter image description here

Just below the emitter plane I closed the cylinder with a face. And checked Size Deflect. Also the cylinder has Collision marked. Now the fluid particles should be blocked by the cylinder / lamp ? But as you can they are not. What should I change to block the fluid particles by the lamp ?

  • $\begingroup$ I am not very skilled at that so I wont give an answer, but you have a parameter to increase the precision of the simulation. You can find it in the physics section of the particles system. Its name is "subframes" and is set to 0 by default. Set it to 2, for instance. The principle is to calculate more simulation steps (here 2+1) during each rendering frame. To say it differently, for each frame (image) calculated, the simulation calculates more than 1 (here 2+1) frames so that it will not miss the collision (or will miss less) $\endgroup$
    – lemon
    Aug 2, 2016 at 11:10
  • $\begingroup$ You can also change the calculation mode : it is found in "integration". By default "Midpoint". But the tooltip says that "verlet" for instance is more accurate. $\endgroup$
    – lemon
    Aug 2, 2016 at 11:14
  • $\begingroup$ I think you are pretty skilled at this .... thanks a lot :) $\endgroup$
    – user13877
    Aug 2, 2016 at 11:14
  • $\begingroup$ Seriously, I am not... but I learn a lot with the questions : ) $\endgroup$
    – lemon
    Aug 2, 2016 at 11:15

1 Answer 1


The most possible reason for that behaviour is non-manifold geometry.

When closing particles within the lamp by filling a face inside of the lamp, you create non-manifold mesh which might be hard to deal with for engine. Particles fly through from the bottom, where the face is created and which should block them.

To make the mesh as manifold one, first delete that inside face. Then you'll need to:

  1. Solidify the mesh (either with Solidify modifier or by extruding geometry in Edit mode and scaling extrusion a bit inside).

    screenshot of solidified mesh

  2. Create a face which will block particles. For that, select edge loop, left from original face, bevel it with Ctrl+B and fill 2 new faces (they will be Ngons, however it doesn't really matter here).

    Beveled edge loop: screenshot of beveling geometry

    Filling new faces: screenshot of filling faces

Particles will fly inside and collide with walls as expected:

GIF of result

  • $\begingroup$ WOW, Mr Zak. That is really a big improvement $\endgroup$
    – user13877
    Aug 2, 2016 at 15:30

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