Mathematica plots a discontinuity in piecewise function that does not exist [duplicate]

I have the following function defined:

IntImpTri[r1_, r2_, r_] := 
  Piecewise[{
    {((4/((r2 - r1)^2)) ((r^2 - r1^2)/2 - r1 (r - r1))), 
     r >= r1 && r < ((r1 + r2)/2)}, 
    {(1/2 - (2/((r2 - r1)^2)) (r^2 - ((r1 + r2)/2)^2) + 
      (4/((r2 - r1)^2)) r2 (r - ((r1 + r2)/2))), 
     r >= ((r1 + r2)/2) && r < r2}, 
    {1, r >= r2}}, 0];

I am using Mathematica 9 and I do not understand why, when I try to plot this function, which is the integral function of a triangle pulse, the figure shows an interruption in the line.

If I try the following command: Plot[IntImpTri[0, 4, r], {r, -1, 5}], I get the following output:

There is a discontinuity around x=2 but the piecewise covers everything!