Detect blending dynamically

Author: dy

src/traces/pointcloud/attributes.js

@@ -75,7 +75,7 @@ module.exports = {
         },
         blend: {
             valType: 'boolean',
-            dflt: false,
+            dflt: undefined,
             role: 'style',
             description: [
                 'Determines if colors are blended together for a translucency effect',

src/traces/pointcloud/convert.js

@@ -174,7 +174,12 @@ proto.updateFast = function(options) {
 
     markerColor[3] *= opacity;
     this.pointcloudOptions.color = markerColor;
-    this.pointcloudOptions.blend = options.marker.blend;
+
+    var blend = options.marker.blend;
+    if (blend == null) {
+        blend = x.length < 100 || y.length < 100;
+    }
+    this.pointcloudOptions.blend = blend;
 
     borderColor[3] *= opacity;
     this.pointcloudOptions.borderColor = borderColor;