Fixing red triangles face inwards

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MysticDarkLord
Posts: 5
Joined: 01 Jan 2016, 19:36

Fixing red triangles face inwards

Post by MysticDarkLord »

Hello,
Is there a method to fix within Kisslicer?
I am merging two stl's for a dual extrusion print, I have done this print before using different software, and did not have this issue, but on Kisslicer I get some segments of one extruder not printing, these are notably red on the model in the viewing window, indicating that they are "Red triangles facing inwards", I don't know what triangles are in relation to the model let alone them facing inwards.
Can I somehow make changes in kisslicer to print these segments along with the others?
Cheers
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EddyMI3D
Posts: 81
Joined: 03 Oct 2015, 17:12

Re: Fixing red triangles face inwards

Post by EddyMI3D »

I think there is no way within Kisslicer.
You could try MeshLab. It's free and can repair some parts.
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PenskeGuy
Posts: 98
Joined: 08 Nov 2014, 18:04

Re: Fixing red triangles face inwards

Post by PenskeGuy »

MysticDarkLord wrote:Hello,
Is there a method to fix within Kisslicer?
I am merging two stl's for a dual extrusion print, I have done this print before using different software, and did not have this issue, but on Kisslicer I get some segments of one extruder not printing, these are notably red on the model in the viewing window, indicating that they are "Red triangles facing inwards", I don't know what triangles are in relation to the model let alone them facing inwards.
The other software probably doesn't even recognize that there is an issue. KS is very intelligent in this regard and identifies all manner of crap that "other software" "has no problem with".

Every shape must have all of its outside surface polygons facing outward. This defines what is the outside and what is the inside of the shape. If some polys are facing in the opposite direction to the others, this will confuse the slicer, as it will not be able to identify the outside and create accurate paths along it.

Triangles are the polygons that make up the model shape. STL file format polygons are all triangles.

MeshLab may work but in order to fix this you probably will need a polygon modeler. Select the errant poly, flip it so that its normal is facing the correct direction along with all of the other polys and save the file.
MysticDarkLord
Posts: 5
Joined: 01 Jan 2016, 19:36

Re: Fixing red triangles face inwards

Post by MysticDarkLord »

Hi,
I tried repairing the mesh within Rhinoceros, didn't make any difference. Not 100% sure what the repair process did either.
Thanks very much for the detailed response on the Poly definition. I understand now what Kisslicer is seeing and now saying :D
I will have to try the modelling software to see if I can flip the surface direction.
Cheers
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voyt
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Re: Fixing red triangles face inwards

Post by voyt »

Try using FLIP command in Rhinoceros. It inverts the normal direction for surfaces, polysurfaces, meshes and single triangles.
To be able to identify the actual normal direction of objects in one of shaded view modes go to:
Tools>Options>Rhino Options>Appearance>Advanced Settings>Shaded(or Rendered, Ghosted etc.)
On the right side panel change: Backface settings = "Use front face settings" to = "Single Color for all bacfaces" (e.g. magenta).
That helps track problems at the time of modelling..
euroreprap.eu
MysticDarkLord
Posts: 5
Joined: 01 Jan 2016, 19:36

Re: Fixing red triangles face inwards

Post by MysticDarkLord »

Hi voyt,
Thanks for the info on using Rhino, I have followed your procedure and understood what it is that I was doing.
The only problem that I have is that Rhino and Kisslicer don't seem to be uniform in the definition of what is facing which way. In Rhino it appears that there are no surfaces which need to be flipped as they all appear normal, in Kisslsicer they appear different.
I wish I understood CAD better.
I have just noticed that the winding order does not match with reference to the interface between sections that appear inside out in Kissslicer, any help with that?
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PenskeGuy
Posts: 98
Joined: 08 Nov 2014, 18:04

Re: Fixing red triangles face inwards

Post by PenskeGuy »

[quote="MysticDarkLord"I have just noticed that the winding order does not match with reference to the interface between sections that appear inside out in Kissslicer, any help with that?[/quote]
Winding order is related to normal direction. Create a poly by selecting points clockwise and normal will face in one direction. Select in counterclockwise order and the normal will face the opposite. Flipping should cure this. In LightWave, the clockwise direction makes polys facing out. I would assume this to be true for all polygon modelers. I have an old Rhino version I can check, but I've never run into any anomalies prior. May also be that the poly was created with the points not being selected in sequence. Get one in the string out of order and the poly will be created and may look okay, but still would confuse an application that delves into the structure as deeply as a slicer does. Best to just whack the poly and recreate.
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