<html>Dear Christophe,<br /><br />Thank you for your invaluable help. I have done that.<br /><br />Best regards, Zuheyr<br /><br />On Saturday, May 23, 2020 09:53 CEST, Christophe Geuzaine <cgeuzaine@uliege.be> wrote:<br /> <blockquote type="cite" cite="8AA28D58-C4DE-4469-B9B3-12FD5C247DF3@uliege.be"><br /><br />> On 12 May 2020, at 17:50, Zuheyr Alsalihi <alsalihi@vki.ac.be> wrote:<br />><br />> Dear colleagues,<br />><br />> I could not easily describe the problem.<br />><br />> A rectangular slab step file that I have generated, attached CG1.step, shows the top and bottom surfaces inward normal.<br />> I am not able to reverse this.<br />> But the surface is there, see Pic1.png. When I create an STL mesh with GMSH gmsh-4.5.6-Linux64/bin/gmsh<br />> these 2 surfaces are not meshed. Can you please help me understand and solve this problem?<br /><br />Somehow OpenCASCADE badly translates surface 5 in the STEP file. See attached .brep of the offending surface: all point evaluations within the surface are (wrongly) evaluated on a plane parallel to the surface, but translated.<br /><br />You should report this bug to the OpenCASCADE developers and attach the STEP file.<br /><br />Christophe<br /> </blockquote><br /><br /><br /> </html>