Review support algorithm

[kakaroto]

The support algorithm is somehow wrong, I don't know yet what's causing this, nor do I know if it's only a display bug or a print bug as well (I will confirm after printing the model, although I expect the print to have the same issue since the slicing is done on the same vtk pipeline), but I can clearly see an issue in how the support material gets inserted for the eiffel tower model.
If we look at this screenshot of the eiffel tower :

We can see that the support is going right through the model, which would make it impossible to remove. There is an issue with almost all of the support pillars, the most obvious one is the one in the middle of the screenshot, going right through the leg of the eiffel tower, but we can also see in the bottom right corner that the support going through the base of the leg is also poking through it. And in the top-center of the screenshot, we can also see the tip of the support cone traversing the first 'floor' of the eiffel tower.
I have checked that the behavior happens on both VTK5 and VTK6. The support algorithm must have a bug somewhere, causing this.

[robotsinthesun]

That's not an actual bug, it's just how the support generation is
implemented.

It creates a point pattern and shoots vertical lines through the model
starting from that pattern. If a line intersects an overhang region of
the model, a support is created at this position.

That's why you see supports going through the trusses of the tower,
eventually hitting an overhang region somewhere above -- which will
create a support that goes through the truss below. For this case,
there's the support height option. With this, you can limit the maximum
height of the supports so these things won't happen.

However, the main issue is, that an object like that Eiffel tower is
extremely hard to support, given all the small trusses. At least the
pattern support that's currently implemented cannot properly handle
this. A better algorithm would probably start at the overhang regions
and walk downwards from there. Do you know how Creation Workshop for
example handles this? They have the ability to manually set supports I
guess.

Additionally, I don't think you need supports for this model. I had an
option to disable supports in an older version and could reimplement
that. For now, you could try setting the model Z position to 0 and
simply setting the maximum support height to something small so no
supports are created.

On 26.10.2016 16:47, Youness Alaoui wrote:

The support algorithm is somehow wrong, I don't know yet what's
causing this, nor do I know if it's only a display bug or a print bug
as well (I will confirm after printing the model, although I expect
the print to have the same issue since the slicing is done on the same
vtk pipeline), but I can clearly see an issue in how the support
material gets inserted for the eiffel tower model.
If we look at this screenshot of the eiffel tower :
eiffel-support
https://cloud.githubusercontent.com/assets/27990/19730536/8110012c-9b68-11e6-8f0c-15fda156f890.png
We can see that the support is going right through the model, which
would make it impossible to remove. There is an issue with almost all
of the support pillars, the most obvious one is the one in the middle
of the screenshot, going right through the leg of the eiffel tower,
but we can also see in the bottom right corner that the support going
through the base of the leg is also poking through it. And in the
top-center of the screenshot, we can also see the tip of the support
cone traversing the first 'floor' of the eiffel tower.
I have checked that the behavior happens on both VTK5 and VTK6. The
support algorithm must have a bug somewhere, causing this.

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