Answer
Better to take a photo of some real undulating fabric – the example you posted is a photograph – a raster image. Inkscape is a vector image editor, best suited to line art/logos – not photographic realism.
However it is kind of possible using the gradient mesh feature now available in Inkscape.
Example of Gradient Mesh
Attribution
Source : Link , Question Author : Sanjay Remanan , Answer Author : Billy Kerr