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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Rendering issue occurs when plotting 3D surfaces at a discontinuity","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\n**Bug summary**\r\n\r\n\u003c!--A short 1-2 sentences that succinctly describes the bug--\u003e\r\n\r\nWhen running the code below to plot the surface for the equation 1 - y/x, the plot works but I get an error and the rendering of the surface breaks when viewed from some angles.\r\n\r\n**Code for reproduction**\r\n\r\n\u003c!--A minimum code snippet required to reproduce the bug, also minimizing the number of dependencies required--\u003e\r\n\r\n```python\r\nimport math\r\nimport numpy as np\r\nimport matplotlib as mpl\r\nimport matplotlib.pyplot as plt\r\nimport matplotlib.ticker\r\nfrom matplotlib import cm\r\nfrom mpl_toolkits.mplot3d import Axes3D\r\n\r\n# Generate the data\r\nx = np.linspace(-1.0, 1.0, 50)\r\ny = np.linspace(-1.0, 1.0, 50)\r\nz = np.zeros(len(x))\r\nx,y = np.meshgrid(x,y)\r\nz = 1 - y/x\r\nz[z \u003e= 5.0] = 5.0            # Clips top of surface\r\nz[z \u003c= -5.0] = -5.0          # Clips bottom of surface\r\n\r\n# place NaNs at the discontinuity\r\npos = np.where(np.abs(np.diff(z)) \u003e= 5.0)\r\nz[pos] = np.nan\r\n\r\n# Create the plot\r\np1 = plt.figure()\r\nax = p1.gca(projection='3d')\r\nsurf = ax.plot_surface(x,y,z, rstride=1, cstride=1, cmap=cm.coolwarm, linewidth=0,\r\n                           vmin=np.nanmin(z), vmax=np.nanmax(z), antialiased=False)\r\nplt.title(\"1 - y/x\")\r\nax.set_xlim(-1.0, 1.0)\r\nax.set_ylim(-1.0, 1.0)\r\nax.set_zlim(-5.0, 5.0)\r\nax.set_xlabel(\"x\")\r\nax.set_ylabel(\"y\")\r\nax.set_zlabel(\"z\")\r\np1.show()\r\nraw_input(\"Press any key to close all plots: \")\r\n```\r\n\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n```\r\n/usr/lib/pymodules/python2.7/matplotlib/colors.py:576: RuntimeWarning: invalid value encountered in less\r\n  cbook._putmask(xa, xa \u003c 0.0, -1)\r\n```\r\n\r\nOdd rendering issues appear:\r\n\r\n![rendering_angle1](https://user-images.githubusercontent.com/17462459/46446053-a0d45980-c7d6-11e8-83a1-bf59b00b3a72.png)\r\n\r\n![render_angle3](https://user-images.githubusercontent.com/17462459/46446200-7505a380-c7d7-11e8-9da3-2109b7f9708c.png)\r\n\r\n\r\n\r\n\r\n**Expected outcome**\r\n\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n\u003c!--If this used to work in an earlier version of Matplotlib, please note the version it used to work on--\u003e\r\n\r\nI'd expect to not get errors and to not see the rendering issue. I am using older versions of virtually everything, and this may be a platform-specific issue. Or I may be using this code in a way it was not intended to be used, in which case if there is a more-correct way to do this I'd appreciate someone showing me how to do it.\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Ubuntu 14.04\r\n  * Matplotlib version: 1.3.1\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): 'TkAgg'\r\n  * Python version: 2.7.6\r\n  * Jupyter version (if applicable): N/A\r\n  * Other libraries: \r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/mattforestyoung","@type":"Person","name":"mattforestyoung"},"datePublished":"2018-10-04T00:15:21.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/12395/matplotlib/issues/12395"}