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I'm Tying to make this animation in which a cookie flies and splashes into a coffee cup, but something's not right. The cookie makes the fall in one and a half secod (If in 30fps) but even at 256 resolution divisions, the coffee in the cup just wobbles very slightly and doesn't even think of splashing. I currently cannot provide the images of the fluid since I freed the bake, but this is the setup:

There is a coffee cup that falls on a table (There is a cup on a plate, and in it there is some liquid which is perfectly fitted to the cup. I added a cuboid as a fluid domain set the resolution divisions to 256, and then set the fluid in the cup as a fluid inflow.) and a cookie flies off a plate and is supposed to splash (If only the fluid did) into the cup.

The cookie falls using keyframes. The cookie and coffee cup are not to scale, the coffee cup about 20 cm in the z,x,y axis (but not a perfect square in dimensions) and the cookie about half as small as the rim of the cup in the x,y axis. Is this enough or is it required to provide the .blend file?

I hope this information is enough. I wan't the fluid to splash when in contact with the cookie. Thanks in advance.

Note: Since blender exchange took hours to upload only 20% of the file, I am providing a wetransfer link which expires in a week. Download from here: https://we.tl/t-OUIKjn5FGL

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    $\begingroup$ What's the dimensions of your cup and cookie? How does your cookie fall? Physics or keyframes? Also, it might help to provide a blendfile via blend-exchange.com $\endgroup$
    – haarigertroll
    Commented May 20, 2021 at 15:08
  • $\begingroup$ @haarigertroll The cookie falls using keyframes. The cookie and coffee cup are not to scale, the coffee cup about 20 cm in the z,x,y axis (but not a perfect square in dimensions) and the cookie about half as small as the rim of the cup in the x,y axis. Is this enough or is it required to provide the .blend file? $\endgroup$
    – Yousuf Chaudhry
    Commented May 20, 2021 at 15:17
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    $\begingroup$ without blend file you will be asked a lot of questions....and even then you might not get a good answer. blend file would speed up the process by far. $\endgroup$
    – Chris
    Commented May 20, 2021 at 16:57
  • $\begingroup$ @Chris Ok, I'll just provide a .blend file with only th coffee cup and the cookie (Since I don't want to privide my whole scene) but any sliding animations will look weird since the scene won't be there. $\endgroup$
    – Yousuf Chaudhry
    Commented May 20, 2021 at 20:13
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    $\begingroup$ By the way, it took forever to upload on Blend Exchange... come on, 520 MB? Maybe you should have made a stripped down file where only the necessary parts are contained... we don't need curtains and all that to test the simulation. $\endgroup$
    – Gordon Brinkmann
    Commented May 21, 2021 at 9:37

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Your cookie would have more effect on the coffee if you had the option Use Effector enabled, like you have on the cup, saucer and spoon. Maybe increase the Sampling Substeps to make the simulation calculate more accurate. And as I said in the comments, the coffee fluid should be set to Geometry, not Inflow. Perhaps it would also help to simulate a bit faster if you disabled the particle system for the sprinkles on the cookie.

fluid sim effector

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  • $\begingroup$ Wow, thanks! It's a very nice splash now. But unfortunately the liquid bursts through the cup even though it has a surface thickness of 0.6 in the fluid settings. $\endgroup$
    – Yousuf Chaudhry
    Commented May 21, 2021 at 11:38
  • $\begingroup$ Another question is that: will increasing the resolution divisions make the coffee loke more thin? And how should I stop the coffee from wobbling too much before contact with the cookie? $\endgroup$
    – Yousuf Chaudhry
    Commented May 21, 2021 at 11:55
  • $\begingroup$ I think that's exactly your problem - the Surface Thickness is added distance to the mesh to be considered as effector (hover your mouse pointer over the value, it explains what it's good for), and since your coffee is directly touching the cup, this 0.6 additional distance are then overlapping with the fluid - which means your liquid is inside the cup walls so they are not blocking its movement. Even with a Surface Thickness of 0 which would only use the direct mesh as effector you could have this problem, since the fluid is touching the cup so due to resolution there can be overlaps. $\endgroup$
    – Gordon Brinkmann
    Commented May 21, 2021 at 11:56
  • $\begingroup$ No, it wouldn't make the coffee necessarily look more "thin", it is more detailed, finer. Maybe that's what you consider thinner. But in terms of viscosity, a higher resolution doesn't make it thinner, only more precise. Fluid simulation is quite complex, we cannot discuss all settings and effects here, what I usually do is making lots of tests with different settings to see how it affects the simulation - before making a longer animation with multiple effectors and moving objects etc. About the wobble: why shouldn't the coffee wobble? With the cup moving down before this would be normal. $\endgroup$
    – Gordon Brinkmann
    Commented May 21, 2021 at 12:03
  • $\begingroup$ Ok, thanks for explaining. But, I still don't undurstand that at a surface thickness of 0.6 when the cookie splashes into the cup the liquid does splash, but along with that it also decides to start flowing out of the walls of the cup. how should I fix that? $\endgroup$
    – Yousuf Chaudhry
    Commented May 21, 2021 at 12:07

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