I am trying to generate a race track in Vertex Shader(constraint) and only using B-Spline/Bezier/Hermite curves. My problem is that when i try to widen the obtained curve by translating another instance of it (lets say translate the x value), at certain turns, the road gets thinner.
As input, i can only have a certain number of control points/knots with which to generate a 2-degree closed(start point = end point) curve B-spline. The closed curve (translated on Z) is shown in the picture attached. The camera is positioned right above it. Every vertex from the curve has Y = 0, seeing how the track is flat without any height(no perspective view).
Is there any possible way to keep the road's width on all its sections?