showcase mesh3d cmin & cmax in tetrahedra mock

Author: etpinard

test/image/baselines/gl3d_tetrahedra.png

@@ -16,6 +16,8 @@
         [1, "rgb(0, 0, 255)"]
       ],
       "intensity": [0, 0.33, 0.66, 1],
+      "cmin": -0.5,
+      "cmax": 0.5,
       "colorbar": {
         "x": 0,
         "title": "for colorscale + intensity tetrahedra",