Am 05.08.2020 um 20:19 schrieb William F Pokorny:
> On 8/5/20 12:46 PM, MichaelJF wrote:
> ....
>> Now I bought a new machine and thought that this open issue would be a 
>> very nice test (core i7 vs. core i9). I rendered the image due to 
>> Clipkas suggestions with diffuse albedo 0.5,0.4 on all balloons. It 
>> has an little bit different mood since the colouring of the balloons 
>> is more visible in the distance. The backside illumination has a 
>> severe drewback: it doesn't work with the colour Blue.
> 
> Welcome back! I've been otherise hacking at the source code today so 
> took a quick look at the related code on seeing your post.
> 
> I don't see anything obvious against blue. My guess is it's that the 
> blues of your balloons are quite dark. When the code multiplies the dark 
> blue value by the backside value*(light * etc) there just isn't much of 
> an adder. Dark+dark still ends up pretty dark - more true if your light 
> source doesn't have much blue in it; If it's flame colored.
> 
> I've played a little with making the backside values larger than they 
> 'should be' but probably that cheat won't work well with, for example, 
> your world map where the bottom looks to be mostly white-ish. Maybe just 
> brighten the blues some on balloons with a lot of dark blue <1,1,2>*...?
> 
> I like the image. It reminds me of a balloon festival I attended a 
> couple times, now 20 years or more ago. Time flies.
> 
> Bill P.
Hi Bill, thanks for your looking into the codes. I can report my results 
only. The balloons in the enclosed image are all rendered with

#declare BText11 = texture {
    pigment { color Red }
    #if (TransparentTex)
       finish { diffuse albedo 0.55,0.4 }
    #end
}

at the position of the red balloon in the original image. Red exchanged 
to Green or Blue from colors.inc of course. Green seems to be most 
addictive to backlight illumination. Blue seems to be ignorant to this 
feature. Without the albedo I got similiar results.

I wanted to report my observations, I cannot see an urgend need to 
investigate this issue. Seems, I'm the first after the release of this 
issue who noticed this.

Best regards
Michael

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