slicing aberration on should-be-homogeneous surface

petaflot commented 6 months ago

Cura Version

Prusa Slicer Version 2.7.1

Operating System

Gentoo GNU/Linux

Printer

custom build

Reproduction steps

slice STL from #18942 with layer thickness 0.3
check second layer

Actual results

see screenshot attached

Expected results

the second layer should be a homogeneous surface : the model was crafted so it would happen

Add your .zip and screenshots here ⬇️

slicing_aberration

petaflot commented 6 months ago

Thanks for the report. It looks to me that your "Initial Layer Height" is interfering because of the way the model is designed. With the Initial Layer Height at 0.15 (same as the layer height) the problem goes away. Here is layer 2 of that project.

@GregValiant your reply is not making sense, it seems you have not understood the issue : if you take slice of my model between 0.3 and 0.6mm, you will see it is solid. with 0.15mm slice thickness, check layer number 4 it should be the same as my layer 2.

also, regarding this "second-layer" issue you should have answered not on #18942 but here (they are quite unrelated issues, it just happens that the model exhibits both). and it just happens to be the second layer precisely because of the way the model is designed : if I wish, I can make this bug (rather, a limitation that shows a problem in the slicing algorithm and impacting probably both the slicing performance and the print times) appear on any layer, any number of times.

GregValiant commented 6 months ago

This is the Ultimaker Cura Github. PrusaSlicer I'm sure has it's own place to report bugs. There are settings that exist in both programs and there are settings that are unique to one or the other. Each piece of software was written by different people. I'm sure they are not the same but I will grant that there are likely similarities.

You did not supply a Cura project file which is necessary to investigate a problem. When I slice the referenced model from that other report, and I use my setting profile and my Ender as the printer, the problem you show in the image in this report does not occur at all.

If you have a problem with PrusaSlicer please fill out a bug report on their site. If you have a problem with Cura then please include a Cura project file. Right now I still don't see a bug here. The "pre wall" constructs on whatever layer is directly below the start of the walls can be tuned out so they don't occur.

I must use the file from the other bug report because it's all I have to work with. This is my standard PLA profile but with a 0.20 Initial Layer Height and a 0.15 Layer Height.

Layer 1

Layer 2

Layer 3

Layer 4

Layer 5

petaflot commented 6 months ago

ok, so far nothing to argue about your comments. maybe you can explain what is the point of the pre-wall feature, but if you can't or won't that's OK with me.

however:

from what I gathered, arachne engine was initiallydevelopped by/for cura, then others started using it
I could find very little if no information at all on how to configure arachne ; I couldn't eve find where the source is hosted (TBH I didn't dig into the source of either Cura or Prusa or Repetier or Octprint or whatever else, because those are GUIs and - if properly coded - should be engine-agnostic)
so far, the best help I've got was from the discord on the printer firmware discord server : doesn't that seem a little odd?
I would hope there are not dozens of implementations of arachne, as that would be a waste of time sand effort

So I would really appreciate to have more info on where to get help specifically for arachne engine, where is the official documentation and where to find the source (because ultimately there is no better documentation and because I might want to contribute)

cheers

GregValiant commented 5 months ago

PrusaSlicer, Orca, and Bambu have a common base (Slic3r?). Cura does not share that. Any two people given a problem to solve with software AND a clean sheet of paper will undoubtedly come up with different ways to accomplish the goal. Since the starting points for each piece of software was different (no clean sheet of paper), and since the companies compete with each other, and since the people involved are different, I would not assume that there is any commonality in the implementation of "Variable Line Width" between PrusaSlicer and UltiMaker Cura. The name "Arachne" may be a left over from a third party who may have originally come up with the concept.

If someone more knowledgeable in the nuts and bolts of Cura sees this, maybe they will respond and they can point you in a direction. I'm not that person.

Ultimaker / Cura