On 6/14/23 09:27, Chris R wrote:
> I would expect to see some variation in the color in that region due to light
> traveling different distances based on the camera angle, but not a complete drop
> out.
> 
> Any idea why this might be happening?

My guess is the top of the liquid shape is open - or for some reason 
effectively open as traced.

The interior fade function - unlike media - works correctly only when 
the interior shape is "clean." Meaning there is a clearly defined pair 
of surfaces of the interior shape defining the distance. The second 
surface also provides the starting color(a) ahead of the fade to color 
calculation.

(a) - Some exceptions apply.

Aside: This very likely also why there is no fading to color in front of 
the green axis cylinder.

Both the fade and colored-transparency images posted indicate there is 
no second surface. Why that might be, I don't know.

An interesting experiment would be to replace the liquid shape with a 
sphere. My guess is that will work OK except perhaps where rays are 
nearly tangent to the sphere's surface.

Bill P.

Aside: It looks to me like there might be some other noise in the posted 
images too - or maybe it's just "floaters" compliments of my old eyes. 
:-)

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