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Walls vs top and bottom layers


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Posted · Walls vs top and bottom layers

When rotating a design for printing,  does it change what Cura considers the outer walls and top/bottom layers?  For example, if I take a box and rotate it on its side for printing, will the side of the box that now sits on the build plate, be considered the bottom layers by Cura?

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    Posted · Walls vs top and bottom layers
    4 hours ago, Rvalecruz said:

    will the side of the box that now sits on the build plate, be considered the bottom layers by Cura?

    Yes.

     

    Cura does multiple steps.  One of the early steps is to "slice" which means cura takes each of the layers and represents a plane and intersects that plane with all the triangles in the STL file (an STL file is an unordered collection of triangles - there is no information in there that says which triangle goes with which).  This is done *after* the rotation that you specified so the triangles are already rotated into their new postitions.

     

    At this point (for each slice) cura has a huge list of straight lines in 2 dimensional space (because we intersected with a plane.  Those randomly ordered lines are then linked up into loops.  The edges of those loops are considered the WALLS even if they are "holes" inside the part.  At the same time cura tries to figure out which side of these loops are inside versus outside.

     

    The TOP/BOTTOM areas are figured out differently - obviously everything printed in the very first slice is "bottom" but there can be "bottom" portions half way up the print as well.  TOP/BOTTOM is figured out in 3 dimensions.  Walls are figured out in a single 2 dimensional slice.

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