Hi Jordan,  I did not notice the wedged shape of the white slab. I do not see that the difference in the two renders as anomalies, but I see it as an anomaly, if the expectation is that the white shape would be cubic, (but when using numbers near the limits, of fp accuracy in openscad/whatever, who knows?) I translated the openscad code into my software, and it works exactly I would expect, no wedge. I think, the error in openscad, is due to it not sensibly handling vertices, with small differences. If you difference a shape, and intersect the shape, there is no guarantee that the vertices match at the common face. Altering the eps, in the original openscad code, alters the direction of the angle. I may export the stl from openscad, and try and see what the mesh is doing. I've attached the output of my cad as a ply file, also my code (with the scad commented out), just to show the numbers are the same.(but syntax different.) .On 12/05/2026 18:49, Jordan Brown via Discuss wrote: > On 5/12/2026 10:40 AM, Cory Cross via Discuss wrote: >> On 5/12/26 5:25 AM, Mark Erbaugh via Discuss wrote: >>> There are no flickering artifacts in either the preview or the >>> render. As suggested in the wiki cite, the code already includes the >>> epsilon (eps in the code) offset. >> There is flickering in the Preview. Just tried it myself. > > Might depend on the graphics stack.  I don't get any. > > > (And yes, it's an anomaly.  Any time that the visual presentation > doesn't match the theoretical result is an anomaly.  That doesn't mean > that we can do anything about it. The previewer is vulnerable to some > anomalies; the renderer is vulnerable to different anomalies.) > > > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email todiscuss-leave@lists.openscad.org

I haven't tried the code, but if it is an epsilon issue, your epsilon is too small. I use 0.05. On Tue, May 12, 2026, 1:52 PM nop head via Discuss < discuss@lists.openscad.org> wrote: > When you do the intersection the eps bit is removed because it is > outside the other shape. All the bottom surfaces are then coincident. > > On Tue, 12 May 2026 at 18:49, Jordan Brown via Discuss < > discuss@lists.openscad.org> wrote: > >> On 5/12/2026 10:40 AM, Cory Cross via Discuss wrote: >> >> On 5/12/26 5:25 AM, Mark Erbaugh via Discuss wrote: >> >> There are no flickering artifacts in either the preview or the render. As >> suggested in the wiki cite, the code already includes the epsilon (eps in >> the code) offset. >> >> There is flickering in the Preview. Just tried it myself. >> >> Might depend on the graphics stack. I don't get any. >> >> >> (And yes, it's an anomaly. Any time that the visual presentation doesn't >> match the theoretical result is an anomaly. That doesn't mean that we can >> do anything about it. The previewer is vulnerable to some anomalies; the >> renderer is vulnerable to different anomalies.) >> >> >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org

 When you do the intersection the eps bit is removed because it is
 outside the other shape. All the bottom surfaces are then coincident.

On 5/13/2026 6:15 AM, Ari Diacou via Discuss wrote: > I haven't tried the code, but if it is an epsilon issue, your epsilon > is too small. I use 0.05. It is an epsilon issue.  It is not that the epsilon is too small.  Set it to 0.5 and see that the problem remains. The issue is exactly as nophead says:  the intersection removes the "epsilon" slice, making the two faces coincident. > On Tue, May 12, 2026, 1:52 PM nop head via Discuss > <discuss@lists.openscad.org> wrote: > > When you do the intersection the eps bit is removed because it is > outside the other shape. All the bottom surfaces are then coincident. >