Enabling transparent webgl draws for scatter3d trace when colors are transparent

[archmoj]

Fix #3492
3D Scatter transparency not activated by marker.color or marker.line.color as well as line.color and errorbars alpha channel.
This is fixed here by patching gl-vis modules.
@plotly/plotly_js

[etpinard]

Hmm. How does this relate to #3138 ?

[archmoj]

Hmm. How does this relate to #3138 ?

Good call.
This PR does not touch gl-mesh3d opacity issues. There is actually another PR on gl-mesh3d repository related to volume trace.
But yeah as discussed we may improve opacity in gl-vis modules in other PRs next.

[archmoj]

@etpinard are you interested to include this in 1.44.3?

[etpinard]

I'm confused by your answer in #3496 (comment)

Have you done any before/after benchmarking?

[archmoj]

OK. In this PR we only activated the alpha rendering channels for those 3 gl-vis modules in case of colors being in rgba format with any alpha less than 1.
If the colors were passed in rgb or they all have alpha equal 1 the alpha channel won't be activated.
Yes I could do a bench-marking next.

[archmoj]

Before codepen.
After codepen.
Both gave me around 1025ms for 10K points.
However; the improvements in the quality of graphs are notable when rotating or zooming in.
Hope it may help.

[etpinard]

Hmm. Are those markers really transparent:

?

[archmoj]

I think some of them are transparent.
Here is the same codepen with fewer points and large markers.

[etpinard]

Ha I see, this is "opacity" from the "a" in rgba. So we're not talking about "true" opacity but "whitening" opacity (see https://github.com/plotly/phoenix-integration/issues/10#issuecomment-164824843 for a past discussion on the topic).

This PR seems like an ok fix for #3492 🎉

I do have one question for @archmoj in -> gl-vis/gl-scatter3d#16 (comment)

[etpinard]

Cool. 💃

Let's get this in for 1.44.3 !