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Liquid Emission unlimited
Confirmed, NormalPublicBUG

Description

"Surface Emission" value ignored I suppose, see the screenshot and the project file below:


That's looks the same or almost same for "Surface Emission"=1,10,100,...

Blender Version 2.90.0 (2.90.0 2020-08-07) on MacOS Mojave.

Event Timeline

Jacques Lucke (JacquesLucke) changed the task status from Needs Triage to Confirmed.Aug 18 2020, 11:02 AM
Jacques Lucke (JacquesLucke) changed the subtype of this task from "Report" to "Bug".

It does not seem to be completely ignored. I do get small differences. However, it's still a bit weird imo. Looking at the code, there seems to be special behavior when the Surface Emission value is set to zero. Also the relation between the emission value and the surface distance is not quite clear to me. Not sure if there is something wrong in the code, or if just the tooltip has to be improved.

@Sebastián Barschkis (sebbas), please have a look.

Maybe related commits: rBcda81d5a4d39: Fluid: Enforce minimum thickness to planar flow / effector objects, rB33317b464777: Fluid: Fixes for flow objects and initial velocities

@Alexey (MBG) Can you rephrase the question? I am not sure which part is problematic.
The "surface emission" value is used to emit additional fluid a bit further away from the surface. A value of 0 will therefore not result in no emission.

Also, note that when changing the "surface emission" value, the cache will not be invalidated (this is a known issue with emitter settings in general right now).

Closing for now. I am happy to look into this again with additional information.

@Sebastián Barschkis (sebbas) What additional information do you required? Try to set the surface emission to zero and invalidate cache and for zero-volume plane object we can see the emission as on the screenshot above. Why is it possible? Try to increase the surface emission value and invalidate the cache and the emission is the same or almost the same as before. So what is means the surface emission? We can't control an object emission by the surface emission parameter.

For liquids, the surface emission value was just used to simulate additional thickness. So a value of 0 just does nothing, a positive value adds some area around the flow object that will be used for emission.
However, I can see how this is a bit confusing: A surface emission value of 0 in a smoke domain effectively turns off the emission.

So assume that's why it's confusing? I am happy to adjust this.

@Sebastián Barschkis (sebbas) Please explain how much is volume of a planar object for you? I sure it must be zero and flow emission from zero volume needs to be zero too. But it works different. Sorry, I absolutely don’t understand how a finite flow emission coefficient multiplied by zero volume can produce non-zero emission. For now, zero volume produces flow emission and that’s nonsense for me. So, the flow emission doesn’t work properly and it’s unpredictable because there is no math to calculate it.

Planar objects where defined to have some thickness by default. The reason for this was that some users found it confusing if planes don't automatically emit fluid.
However, I can see how this is not ideal for everyone. Will adjust so that the surface emission value for liquids behaves more like it does for smoke flow objects.