@smartavionics So I've done some testing on your latest build with good results. I also have a few issues, questions, and requests.
First, the bridging performance over infill is now very good. I still have some tuning to do, but first few prints were night and day compared to the official cura.
First, here's the .3MF I've been testing with. Test print is an easter bunny chocolate egg dispenser. 0.6 nozzle, 0.3 layer height, 70mm/s ish.
Bridging over infill is working much better now. That's over 10% gyroid infill. The second layer over the infill was basically 100% sealed up. I did another print with 5% infill and it wasn't quite as good but with some more tuning of the bridging parameters I think I can get it pretty much perfect.
Which leads me to my first question, What is the bridging flow parameter a percentage of? Is it a percentage of the flow rate set in material, or is it a percentage based on 100% flow in the material section?
Next question, The overhang detection and slow down is working well, but it doesn't seem like the bridging fan speed is being applied to these sections? Shouldn't it be?
Next I have a few issues that I'm not sure are related to the bridging over infill or what.
First is that bridging was not being applied over the eye slots here on the bottom of the model. It was just exposed to the internal infil. This did not happen with the official cura 4.0. I tried changing settings to see if I could get it to show up but nothing. Also note the over extrusion. We'll get to that next.
Next issue is some excessive over extrusion on these curve sections.The extruder is tuned, and the other parts of the print are not over extruded. This is the base of an internal tube that lets chocolate eggs roll through. It is above the sparse infill. The over extruded sections are made up of very short solid fill zigzag moves and go extremely slowly. The requested speed is 35mm/s and the achieved speed as shown in the Duet Web Control is only 15mm/s or so. So it's not able to get up to speed on the short moves as it seems to be using the slower jerk and accel settings I had set for bridging. Whatever the reason, it just gets all blobbed up and eventually the nozzle catches and causes layer shifts. Perhaps you can tell from the .3mf what settings are being applied here and what would need to change to get the over extrusion under control.
That appears to be a second layer of bridging being put overtop the first layer.
In the preview it seems like it's using the bridging parameters for these solid layers, or at least the speed setting, and maybe the higher flow, even though it applies it to layers that aren't above sparse infill. Maybe my sparse infill threshold values are weird?
By comparison, In the official Cura 4.0 it only bridges on the open section above the bed, and just uses the solid infill speed for the layer bridging over the sparse infill on up until it gets to the top most layer that uses the top infill settings. It still gets broken down into small rows of zig zag and topfill when it gets to those layers.
The issue here is triggered by the geometry of the tube section. It's applied top/bottom layers as well as the perimeter values and additionally some bridging all in tiny sections. It would be great if this situation could be detected and handled a little differently.
In Slic3r there is the Ensure vertical wall thickness option which replaces the solid layer sections with some gap fill that scrubs along the edge of the perimeter walls to give it a bit more thickness for the vertical section. Also, if there are two sections of solid infill side by side, say top solid fill and top/bottom solid fill, Slic3r will extend the top fill to replace the sectio that would still be internal solid fill. This creates a much larger contiguous area so the zigzags aren't all cramped up and causing over extrusion.
So then, is the bridging over infill setting being applied erroneously in these areas? Is there anything in the existing parameters that can be changed to reduce this over extrusion? Is there any way these situations could be detected and handled in a situation similar to how slic3r handles it?
And finally, the small feature speed reduction feature. This circular part is the pin for an print in place hinge that lets the bunny head flip up. It builds up from a cone to a 1mm rod and then back up into another cone that eventually gets bridged over to the rest of the head to capture the hinge. It worked really well up until there was some solid infill in the middle of the small feature. It doesn't seem like the speed reduction is being applied to the solid infill. I've tried increasing the small feature size and it does change what gets affected, but it seems to only apply to perimeters. Needless to say, even though the perimeters print nicely, once it gets to the infill at 70mm/s it breaks the pin instantly. Could the small feature detection be expanded to include the entire island if the whole size fits within the feature size?
I think that's all I had. Sorry for the super long report.
Thanks for all your hard work on these builds. You've managed to make a sizeable dent into my feature wish list.