GL_TRIANGLES and GL_QUADS ->Problem with Smooth Shading..

yes im sure many of you have experience this before. i am making a heightmap with GL_TRIANGLE_STRIPS, i have enabled smoothing but down the middle of each quad(really this is 2 triangles) you get a defined line right down the middle. try it with just a 2D Quad also… try to put different colors on the Quad and see if you dont this line down the middle of it. actually this line goes in a diagonal direction. so can anyone help me?

the only way to get rid of that is by introducing a new vertex in the center. It’s the exact same problem in color space as trying to fit a plane to 4 nonplanar points in R3.