2
$\begingroup$

I have a mesh plane which is a glass object, transmission and alpha all the way up, which means its 100% opaque.

Whenever I use a lighter colour the emission shader goes through the glass, but when I use a dark colour as shown in the example Black, the emission wont shine through, so I lower the alpha to get some emission going through.

Why does the black or dark colours effect the emission luminance once placed over it, since the alpha and transmission is all the way up?

enter image description here

$\endgroup$
  • $\begingroup$ Hello :). In Cycles and Eevee, the darker the glass, the less light gets 'through'. Fully black glass won't let any light get through. $\endgroup$ – Jachym Michal Oct 18 at 15:04
8
$\begingroup$

Reframing the idea behind “Alpha” as occlusion should make the idea clearer, where “Transmission” is a degree of filtration.

The 0.0-1.0 range in alpha represents the degree of occlusion from 0% to 100% in a properly encoded image, while the RGB represents the quantity of emission. Something can be completely unoccluding (0.0 alpha, 0%) and emitting (nonzero RGB units), as well as completely occluding (1.0 alpha, 100%) and not emitting (0.0 RGB units).

Transmission represents the ratios of light permitted to pass through the object. 0.0 would indicate that 0% of the given channel is permitted to pass through, while 1.0 would indicate 100%. In this way, Transmission behaves like a light “filter”.

In this way, the RGB values are pulling double duty, both as the emission for the alpha component and as the filtration mechanism for Transmission. It is worth understanding that in different contexts the values present in the three channels can mean different things, and it's not always a "colour" per se.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Great information, thank you. $\endgroup$ – blender breath Oct 19 at 11:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.