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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"BUG: plot_surface ignores lightsource when cmap/facecolors are not specified","articleBody":"Three different, undocumented, cases that I think should be the same:\r\n\r\n1. `plot_surface(..., shade=True, lightsource=..., cmap=..., facecolors=\"garbage\")` -  uses `LightSource.shade`, which does some messy and unnecessary trig in `LightSource.hillshade`, using the orientation of the lightsource.\r\n\r\n2. `plot_surface(..., shade=True, lightsource=..., cmap=...)` -  uses `_shade_colors`, which does a more sensible vector-based approach, but hard-codes a `[-1, -1, 0.5]` normal vector, rather than respecting the lightsource direction.\r\n\r\n3. `plot_surface(..., shade=True, lightsource=..., facecolors=\"garbage\")` - as above\r\n\r\nRegarding (2), I think that there is a typo in `axes3d.py`, and this change should be made:\r\n\r\n```diff\r\n         # Shade the data\r\n-        if shade and cmap is not None and fcolors is not None:\r\n+        if shade and cmap is not None and fcolors is None:\r\n             fcolors = self._shade_colors_lightsource(Z, cmap, lightsource)\r\n```\r\nIt seems dumb to only calculate face colors if the user already asked for different ones.\r\n\r\nRegarding (3) - I think it would be useful to unify the shading into a normal-vector based approach, which I might try in a later patch\r\n\r\n\r\n","author":{"url":"https://github.com/eric-wieser","@type":"Person","name":"eric-wieser"},"datePublished":"2017-07-14T19:07:44.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/8877/matplotlib/issues/8877"}