I have application to draw thick lines. It is drawn using triangles. The problem is one side of triangle is not straight. This is the image showing the drawn picture:

These are the vertices:

x 0.5

y 0.8500000238

x 0.5

y 0.150000006

x -0.1499999762

y 0.150000006

x -0.5

y 0.8500000238

x -0.8500000238

y 0.8500000238

x -0.8500000238

y 0.5 float

x -0.8500000238

y 0.5

x -0.1499999762

y 0.150000006

x -0.8500000238

y 0

x -0.150000006

y 0

And the indices: 0, 1, 2, 0, 2, 3, 4, 3, 2, 4, 2, 5, 8, 7, 9, 8, 7, 6

This does not happen only with these vertices, but also if I draw it with other vertices. I have no idea why since the y coordinate does not change.