Why can I see through the model as if the triangles are transparent in the Exact Surfaces phase?

If you see the Boundaries, Feature Lines, and Constrained lines through the model as if the triangles are transparent this is because the “lines” are not displayed on the surface properly. To correct this try selecting Use Polygon Offset in Options.

Click on the Application button and then Options.

Select Use Polygon Offset in Options>Graphics>OpenGL.