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Boolean modifier still processed when bypassed (when using Animated Booleans)
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System Information
Windows 8.1 Home 64 bit
Nvidia Geforce GTX 970
Intel Core i7-5930K CPU @ 3.5 GHz

Blender Version
Broken: (2.79 5bd8ac9)

Short description of error

So this might be a known issue/limitation that will be fixed in 2.8, but in 2.79, I've noticed that having a boolean modifier completely disabled (no render, no preview) still runs in the background when its target is an animated object. This actually more than halves the playback framerate of the 3D window. If the modifier has no target, or the object is non-animated, framerate is fine.

Thanks for your time in reading this. Please let me know if there's a known workaround for this, or if this is already something of the past with the new dependency graph of 2.8 (I have not tried the 2.8 builds yet).




Event Timeline

ronan ducluzeau (zeauro) triaged this task as Needs Information from User priority.

Please share maximum pieces of information.
How did you notice that ? Can you share measures of the issue ? Does it happen when blender is launched with --enable-new-depsgraph comand ?

Please upload a simple .blend demonstrating problematic behaviour.

Thanks Ronan;

Interestingly, in the test project I wasn't able to trigger the excessively slow behavior from the animated boolean object until after I added two 16 vertex circles into the plane object. There is very poor playback even with no Boolean modifier on the object. In my original project, though, removing the boolean modifier made things run smoothly even with those 2 circles (however there was only 1515 items in the array vs 1800). It seems as the array decreases, framerate increases, so it must be the array modifier that is making the biggest hit, and in the original project the bypassed boolean modifier was just pushing it over the edge. It seems strange considering the system specs it's running on (6 core, 32 GB ram, GTX 970). Here is the test file:

Thanks for your time.

ronan ducluzeau (zeauro) claimed this task.

This is no more an issue with boolean modifier but it turns into a feature request about array modifier performances.
We could resume it as "At a count above 1000 duplicates, array modifier becomes slow."
Of course, better performances of viewport and modifiers are a target for 2.8 release.
But it is not necessary to keep a reminder about a threshold value to expect developers to try to repel it.

So, I am closing the report.

Array modifier was not initially designed to handle as many duplicates as particles.
Here, it generates an heavy mesh of almost 120 000 virtual faces. At this amount, it is generally welcomed to apply modifier.
You can make an incremental save of your .blend file before applying modifier or copy your object, disable its modifiers and move duplicate to an unused layer.
If array modifier is applied and boolean modifier disabled, frame rate is at its maximum with current master.

If you absolutely need to see animation of gap in path, you can also be more efficient by using beveled/taper curves rather than this Array+Curve+Boolean solution.

The better workflow to handle modifiers limitations is a general support issue and not a software error we can investigate.

For general issues, check on support sites such as:

If you still think you have found a bug, please give exact steps to redo the error.

Thanks Ronan for the info and the link about curves.

The test file I submitted was in an attempt to recreate the slowdown as I had first encountered it in my original project. However, in my original project, I am now using an animated material rather than a Boolean modifier to accomplish the effect I need, which works great. The report about the bypassed boolean modifier reducing the frame rate by 50% with 1515 duplicates but when it has no target the frame rate is 100% (even with 1515 duplicates) still stands true in my original project. So yes, the array modifier is generating many faces but the boolean modifier is still incorrectly contributing even when bypassed. It is unfortunate the smaller scale test project I submitted did not reveal this issue.

However, in the future, should I ever need to use a boolean specifically in this way, I will apply the array modifier if it slowing things down.

Thank you again.