add "pad" using max u/v/w norm around cone bounds

... during autorange / scene bounds computation.

- This pad values is a "worse case" solution (i.e. it pads too much
  for most situations), but gives nice visual results (I think).

Author: etpinard

src/plots/gl3d/scene.js

@@ -480,9 +480,12 @@ proto.plot = function(sceneData, fullLayout, layout) {
             var axLetter = axis._name.charAt(0);
 
             for(j = 0; j < objects.length; j++) {
-                var objBounds = objects[j].bounds;
-                sceneBounds[0][i] = Math.min(sceneBounds[0][i], objBounds[0][i] / dataScale[i]);
-                sceneBounds[1][i] = Math.max(sceneBounds[1][i], objBounds[1][i] / dataScale[i]);
+                var obj = objects[j];
+                var objBounds = obj.bounds;
+                // add worse-case pad for cone traces
+                var pad = (obj._trace.data._normMax || 0) * dataScale[i];
+                sceneBounds[0][i] = Math.min(sceneBounds[0][i], objBounds[0][i] / dataScale[i] - pad);
+                sceneBounds[1][i] = Math.max(sceneBounds[1][i], objBounds[1][i] / dataScale[i] + pad);
             }
 
             for(j = 0; j < annotations.length; j++) {

src/traces/cone/calc.js

@@ -28,5 +28,7 @@ module.exports = function calc(gd, trace) {
         normMin = Math.min(normMin, norm);
     }
 
+    trace._normMax = normMax;
+
     colorscaleCalc(trace, [normMin, normMax], '', 'c');
 };

test/image/baselines/gl3d_cone-simple.png

@@ -10,10 +10,21 @@
       "w": [0, 0, 2],
       "sizemode": "absolute",
       "sizeref": 2
+    },
+    {
+      "type": "cone",
+      "x": [1, 2, 3],
+      "y": [1, 2, 3],
+      "z": [1, 2, 3],
+      "u": [1, 0, 0],
+      "v": [0, 3, 0],
+      "w": [0, 0, 2],
+      "scene": "scene2"
     }
   ],
   "layout": {
     "scene": {
+      "domain": {"x": [0, 0.5]},
       "xaxis": {
         "range": [-2, 5]
       },
@@ -23,6 +34,9 @@
       "zaxis": {
         "range": [-2, 5]
       }
+    },
+    "scene2": {
+      "domain": {"x": [0.5, 1]}
     }
   }
 }