3D Scatter transparency not activated by marker.color or marker.line.color as well as line.color and errorbars alpha channel

[jonmmease]

Originally reported in plotly/plotly.py#1416.

The alpha channel of rgba colors seems to be respected by scatter3d, but only if the opacity property is set to something less than 1.

CodePen: https://codepen.io/jonmmease/pen/OdRbdL

var trace1 = {
  x: [0, 1.1, 2.2], 
  y: [0, 1, 2], 
  z: [0, 1, 2], 
  mode: 'markers',
  marker: {
    size: 20,
    color: ['rgba(255, 0, 0, 0.9)',
            'rgba(255, 0, 0, 0.5)',
            'rgba(217, 0, 0, 0.1)'],
    line: {
    },
    opacity: 1.0
    // opacity: 0.99
  },
  type: 'scatter3d'
};

var data = [trace1];
var layout = {
      margin: {
        l: 0,
        r: 0,
        b: 0,
        t: 0
  }};
Plotly.newPlot('myDiv', data, layout, {showSendToCloud: true});

With trace1.opacity: 1.0

With trace1.opacity: 0.99

Could the opacity<1 logic be activated automatically if marker.color includes rgba colors with alpha < 255? Or maybe just if there are any colors specified as rgba period.

[archmoj]

It seems a similar issue existed with lines.
Here is a demo.

[etpinard]

I guess we could activate it for scalar values, but for array marker.color that's whole other story -> #3138