Improve spec_trans documentation

[mturiansky]

Description

It would be nice to be able to specify an RGBA value for the color of meshes.

Preview

I'd like to reproduce the isosurfaces with the opacity shown in (b) and (c) of this figure using fresnel:

Developer

I'd be happy to look into implementing this if someone could push me in the right direction.

[tcmoore3]

@mturiansky is the spec_trans material property not what you are looking for?

[mturiansky]

@tcmoore3 Oh wow, now I feel dumb. That is exactly what I'm looking for. The spec_trans property just doesn't work in the interactive SceneView, right?

[tcmoore3]

@mturiansky I think it should work in a SceneView, but Qt widgets are notoriously finicky, so there may be something weird going on with different versions of different libraries.

[joaander]

spec_trans should work in the interactive scene view. Maybe you are using the Preview tracer? spec_trans only works with the Path tracer. That should be documented somewhere, but it is not. Also, there needs to be light coming from behind the object to pass through the material, so it works best with cloudy or lightbox lighting. There should also be an example dedicated to spec_trans, specifically covering the lighting issues (which are not obvious).

I am reopening this as a reminder to add this documentation.

[mturiansky]

You're correct; spec_trans does work in the interactive scene view. I think the combination of sub-optimal lighting, lower sampling, and relatively low spec_trans value made the transparency not obvious. It wasn't until I generated a static image with good sampling that I could see the transparency.

[github-actions]

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