STL file export, shift coordinates and flip y and z. Intended?

iarUka · 10th December 2023, 12:22 PM

Using AC3D 9.1.0 on linux.
I noticed that an export to STL format flips the Y and Z axis and offsets the coordinates for the vertices to be all positive. Is that intended? If so, why?

How to reproduce:

create a new scene
generate any triangle object in a space close to the origin, make sure at least one coordinate is negative. I used a square and triangulated it.
export to STL, I used ASCII (but that should not matter)
re-import from the same file in the same scene.

The result of this is that the element exported shows up somewhat rotated and translated.

Now I read that STL requires to have only positive coordinates. I also read that this is historic and not required. I do not read anything about the axis flip, but I might not have read the correct sources.

If I modify the STL files to contain negative vertex coordinates, AC3D imports that without problems.

Could we add settings to control that behavior, similar to OBJ files?

10th December 2023, 12:22 PM	#1
iarUka Junior Member Junior member Join Date: Dec 2023 Posts: 2	STL file export, shift coordinates and flip y and z. Intended? Using AC3D 9.1.0 on linux. I noticed that an export to STL format flips the Y and Z axis and offsets the coordinates for the vertices to be all positive. Is that intended? If so, why? How to reproduce: create a new scene generate any triangle object in a space close to the origin, make sure at least one coordinate is negative. I used a square and triangulated it. export to STL, I used ASCII (but that should not matter) re-import from the same file in the same scene. The result of this is that the element exported shows up somewhat rotated and translated. Now I read that STL requires to have only positive coordinates. I also read that this is historic and not required. I do not read anything about the axis flip, but I might not have read the correct sources. If I modify the STL files to contain negative vertex coordinates, AC3D imports that without problems. Could we add settings to control that behavior, similar to OBJ files?