Plotting a 3D surface in Cartesian coordinates from a polar-grid data


I have an irregular grid in polar coordinates, i.e. I have two arrays r[100] and theta[200] that define the grid and an array containing the data that I want to polt, data[200,100]. Is there any simple way to make a surface plot in Cartesian coordinates? Or at least in polar?

So, mathematically speaking, I have a function f(\theta,r) defined on the irregular grid (\theta_i,r_j), i = 1,\ldots,200, j = 1,\ldots,100 (actually, the (\cos \theta_i, \log r_j) grid is regular). And I would like to plot this function in, ideally, Cartesian coordinates. What would be the easiest way to do so? Thanks in advance for any help!