How to get normal vector of any point?

I get the point of intersection line and shape. (I am using IntCurvesFace_ShapeIntersector.)

so, I known U, V, W parameter and point coordinate.

But I don't have any idea for how to get normal vector of this point.

what means of u, v, w parameter??

Somebody help me~!
Thanks.

Francois Lauzon's picture

Hello,
do the following:

TopoDS_Face aFace=intersector.Face(i); // intersector being your IntCurvesFace_ShapeIntersector and i the current index
BRepAdaptor_Surface aSurface(aFace);
gp_Vec ut,vt;
gp_Pnt pt;
aSurface.D1(intersector.UParameter(i),intersector.VParameter(i),pt,ut,vt);
gp_Vec normal=ut.Crossed(vt);

Good Luck,
Francois.