Tree Support Interface Not Generating at Layer 1 For Portions of Models Within the Support Interface Thickness + Distance

[mzhu1113]

Cura Version

Whenever Tree Supports Were Changed to Organic

Operating System

NA

Printer

NA

Reproduction steps

This is replicable by floating any object with tree supports turned on.
Example:
Support Roof Interface Thickness: 2.0mm
Support Top Distance of 0.2mm

Actual results

Any supported surfaces that are within 2.2 + a layer will not have the first layer of the support interface created, instead it starts on the second.

This effect can be more easily seen by tilting any object.

I did not test to see if this affects interfaces over objects when Everywhere placement is enabled.

Expected results

Support interface should be generated on layer 1.

The workaround for this issue would be to place a support blocker, change it to print as support, make it a layer thick, cover the affected area on the build plate.

This issue has been present for a while but I have some spare time to get this reported since we had a print failure that resulted from this.

Add your .zip and screenshots here ⬇️

[GregValiant]

Thanks for the report.
I can duplicate this.
Here I have tilted the model a bit.
This is the first layer. There are just a couple of spots of support.

On the second layer the full interface goes down. It isn't getting any squish.

Project file
19937.zip

[HellAholic]

I get the idea behind the issue, but I would also use common sense when selecting support type for specific models. In such a model, having a tree support doesn't provide a benefit, If you look at the number of interface layers you're printing in the preview, material usage, print time, and the part quality, I don't see why you would want a tree support for such a model. It's practically normal support with few rings placed which might save some filament but so does modifying the normal support density, direction, etc. I don't think I can frame this in such a way that it will not be deferred.

Still, if you have a specific use-case that requires tree support due to the model shape where the normal support is clearly not an option, then there is a discussion to be had.

[mzhu1113]

Still, if you have a specific use-case that requires tree support due to the model shape where the normal support is clearly not an option, then there is a discussion to be had.

I have a lot of models that fit the use case where Tree Supports - Buildplate is much more preferred than Normal-Everywhere like some enclosures being a common one.

In my opinion Tree Supports fulfill two cases:

1. Easier to remove supports; alternative to Normal - Everywhere for ornate models. (In some cases, tree supports would be stronger than Normal!)
2. Lower material usage (which can correlate with time savings)

While the example model is flat on the bottom most of the jobs I have to deal with aren't like that. For example, an ornate cap where the cavity has to be printed downward and Normal Everywhere supports would be annoying to post process. Tree Supports from Buildplate would dramatically reduce scrap rates from my post processing team simply breaking the actual part itself.
Another common example would be helmets where the overhangs gradually slopes away from the bed you'd have 2-4mm of surface area that would not have the interface touching the build plate but changing to Normal-Everwhere would increase material usage and place supports in areas that would be harder to clean even with blockers.

If I come across a model that isn't covered by our NDAs I will share it here but otherwise there is a workaround for this issue but it'd be great not having to spend extra time having to deal with it when you have 50+ models to slice in 1-2 hours haha.