Program visu.exe 
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takes as input
1. a file.off,
2. the corresponding file file.off.4ogl.txt computed with the example program 
	blind.exe from file.off 

it displays an OpenGL view of both the mesh and the ridge lines

 ../../demo/Ridges_3/ridges_viewer data/poly2x^2+y^2-0.062500.off  data/data_poly2x^2+y^2-0.062500.offRIDGES-d4-m4-t3-a4-p0.4ogl.txt 0 0

