I am investigating BREP meshes of extruded shapes, and I find that the
Extrude command create a mesh with the bottom triangles' normals
pointing inward. Is this normal behavior? If so, how do I flip the
normals of the bottom triangles such that the whole surface has
consistent direction?
r1 = 10.0; // inner radius
r2 = 20.0; // outer radius
del = 1.0; // this is triangle resolution
dist = 5.0; // extrusion distance
Mesh.CharacteristicLengthMax = del;
Point(1) = {0, 0, 0};
Point(2) = {r1, 0, 0};
Point(3) = {0, r1, 0};
Point(4) = {-r1, 0, 0};
Point(5) = {0, -r1, 0};
Point(6) = {r2, 0, 0};
Point(7) = {0, r2, 0};
Point(8) = {-r2, 0, 0};
Point(9) = {0, -r2, 0};
Circle(1) = {2, 1, 3};
Circle(2) = {3, 1, 4};
Circle(3) = {4, 1, 5};
Circle(4) = {5, 1, 2};
Circle(5) = {6, 1, 7};
Circle(6) = {7, 1, 8};
Circle(7) = {8, 1, 9};
Circle(8) = {9, 1, 6};
Line Loop(9) = {5,6,7,8}; // outer loop
Line Loop(10) = {1,2,3,4}; // hole
Plane Surface(11) = {9,10};
Extrude {0, 0, dist} {Surface{11};}
This is an "O" shape, extruded to make a donut/torus. The top and
sides have consistent normal, but the bottom is backwards. Any
suggestions to fix this would be appreciated.
Mark
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