Update vertextcolor description to note the range of the values

[archmoj]

Fix #3348.
@plotly/plotly_js

[etpinard]

Hmm. That sounds like an odd mesh3d behavior that doesn't have a correspondence in other traces. Can you confirm?

[archmoj]

Actually there is also this bug #3741 in gl-mesh3d.

[archmoj]

Hmm. That sounds like an odd mesh3d behavior that doesn't have a correspondence in other traces. Can you confirm?

@etpinard It is actually the case for other 3d traces e.g. scatter3d: codepen.

[etpinard]

I'm starting to get a little confused by this issue.

First, see https://codepen.io/etpinard/pen/yrMmpJ?editors=0010 - looks like scatter3d is behaving inconsistently. Colors set as rgb(200,100,150,0.2) don't show an alpha channel in scatter. To show that alpha channel, one has to use the rgba prefix e.g. rgba(200,100,150,0.2). That's probably something we could add to the marker.color attribute description:

plotly.js/src/components/colorscale/attributes.js

Lines 108 to 114 in 1d0acf0

	description: [
	'Sets the', context, 'color.',
	' It accepts either a specific color',
	' or an array of numbers that are mapped to the colorscale',
	' relative to the max and min values of the array or relative to',
	' ' + minmaxFull + ' if set.'
	].join('')

Next, if I'm understanding correctly #3348 is about vertexcolor accepting colors as [1,0,0,1] AND [255,0,0,255] see https://codepen.io/etpinard/pen/rbyXvm and https://codepen.io/etpinard/pen/GPNwYX for examples which yield the same graph using different vertexcolor denominator.

---

Things are a little messy here. So feel free to take this issue wherever you please.

[archmoj]

@etpinard thanks for the review.
You are right. There is a problem with Alpha > 1 not being mapped to 0 - 1 range.
That one should actually be labelled as a bug!

[archmoj]

This should be addressed as a bug.
Closing.

[etpinard]

@archmoj feel free to reopen this PR. 💃 - the issue I noticed in #3688 (comment) about rgb vs rgba colors can be taken care of in a separate PR.