OCCT

# save the initial shape to STEP
stepwrite a S "${imagedir}/${casename}.stp"

# read saved STEP into an OCAF document
ReadStep D "${imagedir}/${casename}.stp"

# get document model as a single shape
XGetOneShape S1 D

# check tessellation metrics of the shape restored from STEP
checktrinfo S1 -face ${nb_faces} -nod ${nb_nodes} -tri ${nb_triangles}

vclear
vinit View1
XDisplay -dispMode 1 D -explore
vaxo
vfit

vrenderparams -shadingModel PHONG
vlight -change 0 -intensity 2.5
vlight -change 1 -intensity 0.3
vcamera -orthographic
vdump ${imagedir}/${casename}.png

Close D -silent
Close D1 -silent
unset S
unset S1

# restore reading/writing tessellated STEP geometry default parameters
param write.step.schema AP214CD
param read.step.tessellated On
param write.step.tessellated OnNoBRep