Hello all,

it seems that this Projection-Algorithm of the class GeomAPI_ProjectPointOnSurf is not working precise enough.

Ich project all poles of a BSPlineCurve onto a cylindrical surface. At first glance, the projected curves seem to be quite okay.
If I zoom the projected points, it is visible, that they never lie excactly on the surface.

I looked at the sourcecode of this OCC-class and found no hint about how to force a greater precision.

Did anyone of you experience comparable results ?


Stephane Routelous's picture


I'm quite sure the curve is correct, but the display of the curve is not.
When you display a curve with OCC, a list of segment is computed according to the meshing parameters you are using ( deflectionAngle, etc.. ).


MCV's picture

Thanks for your answer,

I did not change any deflection...meshing parameters.
I just converted surfaces to faces and splines to edges, to be able to return those data to a TopoDS_Compound for the OCC-QT-Visualizer.
Maybe that is the reason.

Is there another alternative ? Something to ommit the conversion to edges/segments and faces ???

Stephane Routelous's picture

I think there is no other aternative except increasing the deflection to have a better result, but you will only have smaller segments ( more accurate )