Blender becomes... sluggish after a while

So, this is something maybe complicated to explain. But after woprking on a scene with a lot of modeling, animation, particles, rendering, etc, Blender becomes sluggish and even hard to navigate on the viewport.

However, if I copy and paste everything on the viewport into a new open Blender and a new save file, suddenly it becomes 100% better and faster.

Is there any explanation to this? Thanks.

This is a clear sign that the memory gets bloated, however the question is why is not cleared as it normally should.

You can try starting Blender with a debug command line argument just in case you are able to figure out some type of error message or warning.

At first attempt try --debug just to see if something is going on. Another case is to do --debug-memory just in case there is some other type of message.

Only with some sort of investigation it would be made sure that is going on and eventually a Blender developer learns about it.

This is a phenomenon I have observed in Maya and Cinema 4d too.
Somehow something gets messed up and then it spirals out and degrades everything.

Is that a memory leak or whatever they call it, when some function keeps repeating itself in a loop “when it shouldn’t” eating away resources until it comes to a halt and crash ? closing and reopening should fix the issue.

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Perhaps a sign that Blender is now on par with the industry leaders in many cases, it is getting the same problems as those apps. :smile:

In all seriousness though, it could be a leak somewhere. Unfortunately, such a bug will be hard to track down and the devs. at least need to know where to start looking.

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So it gets slow, crashes at random, and generally makes people mad? Congrats Blender! You’re one of the beautiful people now! :smiley:

It is easier to swallow when you know you’re not paying 1000 bucks a year for the privilege of dealing with bugs and crashes (I know there is the indie sub, but take note of the gotchas and other goodies in the fine print). That is more money to eventually use to upgrade your content creation hardware.


How many undo steps do you have configured on your preferences? Did you configure any memory limit? You know that some operations are very memory consuming to keep them in the undo “history” and if you don’t set a memory limit it can easily eat out your memory.

I believe it can be one source of your problem, maybe not. I thought I should mention anyway.

This isn’t at all unique to Blender. Quite a few “intensive” programs wind up doing this after a while. Being a computer geek myself I’d say that there’s probably some obscure “memory leak” problem that no one has tracked down yet. And, with software as internally complex as this one is, they might never. Save very frequently, and every now and then just quit the program and reload.

Many memory problems have something to do with caches of baked animations who are not saved at the disk but stay in the memory. So if you work a lot with particles as you said and don’t save those caches it’s normal to get memory and viewport problems.

Can you elaborate on this, Calandro? How will the user know that this case applies to him, and exactly what do you think that he should do? If the cache is saved to disk, will it thereafter be processed from disk, or will it just get reloaded into memory?

I believe that if you know that your computer has limitations in terms of memory it’s clear that caching to disk is a better option than caching all physics into a memory cache.

When you select the disk cache blender creates a folder on the same directory where you have your blender file saved and when those animations are needed it retrieves that information from that folder and not from the memory.

The user has limited memory and needs to work with lots of physics calculations, this applies to him.

He already said: “working on a scene with a lot of modeling, animation, particles, rendering, etc, Blender becomes sluggish and even hard to navigate on the viewport.”

Well, if he is not saving all this data in disk he will have performance problems after a while.

Not all physics calculations give the option to save the cache to the disk, but I believe those already save the cache into the disk as default, like in the case of dynamic paint.

Thanks for all the messages. I hadn’t the time to try to solve the problem with some of the thoughts, but I will later on. Meanwhile, I’m just working fine on anoter ctrl+c ctrl+v scene, so no problem.