title: How to use colormap in VisPy surfaceplot
body: <p>I'm using <code>VisPy</code> to plot a surface, but the function <code>scene.visuals.SurfacePlot</code> only has the parameter <code>color</code>,without the parameter <code>colormap</code>. Does anyone know how to use <code>colormap</code> in surface plotting? </p>