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I realize the topic is confusing, and not even precisely the problem...
I have a box object as a Birth Volume for Foam and Splashes. If this box is hidden (via Max) , but not excluded from the sim then it affects the liquid as well and acts like a solid object (I did not turn off solid object-- and what I was seeing was that my liquid was not being emitted inside the box-- I didn't test it for collisions, etc.)) even though Exclude Hidden Objects in on for the sim.
So in order to use this a Birth Volume I had to manually add it to the Exclude Objects list for the sim (or make it non-solid I suppose). I found it confusing that the hidden object was affecting the sim with Exclude Hidden Objects on. So I guess what is happening is that objects used as Birth Volumes are internally still evaluated fully. I would expect them only to be evaluated as birth volumes, and not to be used as part of the sim. (IIRC this is how Confine Geometry works-- you can leave it hidden, and not have to manually add it to the Exclusion list).
We are using nightly build 2021012030547 Max 2021.1
I have a box object as a Birth Volume for Foam and Splashes. If this box is hidden (via Max) , but not excluded from the sim then it affects the liquid as well and acts like a solid object (I did not turn off solid object-- and what I was seeing was that my liquid was not being emitted inside the box-- I didn't test it for collisions, etc.)) even though Exclude Hidden Objects in on for the sim.
So in order to use this a Birth Volume I had to manually add it to the Exclude Objects list for the sim (or make it non-solid I suppose). I found it confusing that the hidden object was affecting the sim with Exclude Hidden Objects on. So I guess what is happening is that objects used as Birth Volumes are internally still evaluated fully. I would expect them only to be evaluated as birth volumes, and not to be used as part of the sim. (IIRC this is how Confine Geometry works-- you can leave it hidden, and not have to manually add it to the Exclusion list).
We are using nightly build 2021012030547 Max 2021.1
The specific use case is when you have some heavy or complex geometry that you do not want in your view all the time. If anyone else has any thoughts on whether birth volumes should keep working if hidden, or not, please write here. We thought this was a good suggestion indeed, but if it needs to be re-thought, let's do that...
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