Infill Modifier Bug

[TheRooster13]

Version

Version 2.3.0+win64

Behavior

Using a modifier object to modify the infill % causes changes in the bottom layers that have been specified by height-range modifiers.
In this example, the project settings have 0 bottom layers. A height-range modifier adds bottom layers above 1mm. A modifier object is added to the middle of the part, resting on the build plate. The modifier object only changes the infill %, yet when slicing this model, there is a bottom layer on the first layer.
Expected results: No bottom layer on the first layer.

infill_bug.zip

This is just a sample file. I know this part doesn't need bottom layers anywhere above the first layer, but the real file I'm working on does need bottom layers higher up. I just don't want bottom layers in the first few layers. The real part should be able to be placed over an object, like a cover, so it can't have bottom layers.

Is this a new feature request?
Nope

[bubnikv]

I think the problem here is that the order of application of modifier meshes vs. layer range modifiers is not well specified. You better not overlap the two.

[TheRooster13]

Neither the modifier mesh nor the layer range modifier specify a bottom layer in the bottom 1mm of the model. So it isn't a simple order issue. Also, since the modifiers are modifying different settings, the order shouldn't matter. One modifies bottom layers, the other modifies infill %.
I've also flipped the layer modifier to remove the bottom layers in the first 1mm of the model and set bottom layers to 1 for the entire model and the results are the same.
Likewise, I've set the entire model to 0 bottom layers and then created two layer height ranges. Range 1 from 0-1mm with bottom layers set to 0. Range 2 from 1-210mm where bottom layers are set to 1. Same result.
If I disable bottom layers everywhere, then it works correctly. But if there is a bottom layer anywhere in the model (at least in the overall settings or layer range modifiers) the bottom layer will appear.

[bubnikv]

It seems to work now in PrusaSlicer 2.4.0-alpha1. The order of application of modifiers is:

1. Layer range modifier
2. Modifier volumes in the order they are listed at the side panel, last wins.