Cura: Tree support starts from emptiness

[Chrispizz]

Application Version
CURA V 3.2
Platform
Windows

Qt
N/a

PyQt
N/a

Display Driver
NVIDIA

Steps to Reproduce
1 - Download the STL of YODA BUST on thingiverse
2 - Drop it in CURA V3.2 with Z scale 100.0 ( 10 centimeters )
3 - Apply the "Tree supports"

Actual Results
1 - You will see a lot of support for low points of the chin
2 - You will see under the right ear a support not connected , begining from an empty space , starting from emptiness , with nothing below

Expected results
The support should begin from an other support or from the bed

Additional Information

[ChrisRiddell]

My tree supports look way different to what is generated for you.

But I can get tree supports to generate mid air.

While checking this I noticed it also does not always support unsupported areas.

[Chrispizz]

That you show to us is not "tree support"

[ChrisRiddell]

That is what the "Tree Support" option generates for me.

@Ghostkeeper is my Cura not generating tree supports as per the implementation? (possible bug?)

[Chrispizz]

I don't see your "branches" as a support growing
Your support looks like an envelop

[ChrisRiddell]

Yes it is very confusing, I have tagged the dev that done the CuraEngine PR to get some clarification.

[Chrispizz]

I think that you had not "unchecked" the classical support
Enable only "Tree support" in "Experimental" section

[ChrisRiddell]

Above is with "Support" unchecked, If I enable "Support" as well as "Tree support" I get the same result as above but with normal support within the empty space.

[ChrisRiddell]

So seem to be getting the same type as @Chrispizz now I seem to get the other style depending on model loaded 😕

https://www.thingiverse.com/thing:1074129

[slikk66]

Came here looking for same thing.. I was using 3.2 beta before and got trees, but on 3.2.1 I'm getting non-trees when should be trees.

[Ghostkeeper]

All of your screenshots look like Cura's tree support. Don't worry about it not being tree support, I guess. Cura's tree support does look like it envelops the model sometimes.

ChrisRiddell's last screenshot has support infill though (which defaults to 0% when tree support is enabled and normal support is not).

The tree support generating in mid-air for ChrisRiddell here is sort of a limitation of how the support is generated. I don't really consider it a big problem since it just results in some minor blips on the support and quickly corrects itself in most cases.

The original problem that Chrispizz had though is more serious. I've seen it happen before at colleagues but don't know what causes it. We'll have to investigate that.

The second animation that ChrisRiddell posted about it not supporting some areas is new to me. But it could happen if you set support to be touching the build plate only, when there is no possible path towards the build plate. That's just like normal support.

[Ghostkeeper]

I can't reproduce this with the Yoda model though. What settings are you using? Maybe share a project file?

[DiddiZ]

I get this with a different model Radial_Fan_Fang_5015.stl from https://www.thingiverse.com/thing:2175956/ and Support Placement: Touching Buildplate.

The towers inside the fan duct start in thin air. Granted, there is no way these branches could ever reach the buildplate from inside the ducts, but I think Cura should either complain, or remove these supports entirely instead of letting them start mid-air.

Using Cura 3.3.0-BETA

[ghost]

I am also still experiencing this on 3.3.0 Beta (coincidentally, also trying to print a fan duct). https://www.thingiverse.com/thing:2861755 It's a shame since tree supports generate a much better finish for me while being way easier to remove. I loathe the normal supports.

Note, and possibly related to the bug: If I set the branch diameter angle to 0, I never ever see this problem.

[DiddiZ]

Recently, I ran into this problem so often I basically had to abandon tree support, which is a shame.

I think the following happens (I have by no means looked into the code, so I could be way off): Cura selects the points on the model which shall be supported. Then, working from the top of the model down, Cura tries to plan the trees layer for layer. If for some reason, the tree can't be continued, the tree ends in mid-air. Reasons can be Tree Support Branch Angle (as in there is no way to avoid the model and not violate the angle constraint) or Tree Support Branch Diameter Angle (i.e.: the increased diameter would hit the model).

This is based on how Support Placement: Touching Buildplate and Tree Support Branch Angle affect the chance for partial trees. When increasing Tree Support Branch Angle a previuosly unconnected tree can span around and obstacle and reach the buildplate. Also, when decreasing Tree Support Branch Diameter Angle a collision with the model could be avoided.

If my assumption is correct, Cura should be able to detect if it can not continue a branch (it already does, as it does not continue) , then remove the partial branch (it could not be printed anyway and would just create a mess, but I guess this is the tricky part as branches can affect each other) and possibly display a warning message.

[Ghostkeeper]

It reproduces 100% with tsumeone's model when I set Support Placement: Touching Buildplate on a blank Custom FDM Printer. This way we can debug the issue. The branch diameter angle is a good hint too.

[diegopradogesto]

For Devs.: CURA-5341

[Ghostkeeper]

This is fixed in the next release.