This helped, the blotchiness is acceptable for a still image but still 
jumpy in animation.

Raising the 'scope - yes, good point.

On 06/02/2023 2:14 AM, Alain Martel wrote:
> Le 2023-02-05 à 05:42, m@b a écrit :
> 
> 
> You need to increase the sample value.
> Using the two values version may help.
> Have the pretrace go deeper.
> As for the count, use the two values version for nearest_count.
> 
> Try this version :
> 
> global_settings {
>   assumed_gamma 1
>   #if (Radiosity)
>    radiosity {
>     pretrace_start 0.04
>     pretrace_end 0.0025 // or even 0.00125
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> On 04/02/2023 11:09 PM, Bald Eagle wrote:
>>
>> Nice!
>>
>> Try it with radiosity and using the background image as an hdr light 
>> source:
>>
>> global_settings {
>>   assumed_gamma 1
>>   #if (Radiosity)
>>    radiosity {
>>     pretrace_start 0.04
>>     pretrace_end 0.01
>>     count 200
>>     recursion_limit 3
>>     nearest_count 10
>>     error_bound 0.5
>>    }
>>   #end
>> }
>>
>>
>>
>> #declare Environment =
>> sphere {
>>   0, 1
>>   hollow on
>>   material {
>>    texture { uv_mapping
>>     pigment {
>>      image_map {
>>       hdr "FILENAME.hdr"
>>       gamma 1.5
>>       map_type 0
>>       interpolate 2
>>       once
>>      }
>>     }
>>    finish {emission 1}
>>    }
>>   interior { ior 1.0 }
>>   }
>>   no_shadow
>> }
>>
>> object { Environment scale 1000} // might have to adjust  ;)
>>
> 
> 
> 
> Thanks for that. I am getting a patchy illumination, when I animate it 
> there is inconsistency between frames. Any thoughts?
> 
> The only change I made was to reduce the Environment gamma to 1, the 
> scene was over-illuminated at 1.5.
> 
> m@
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>   // more pretrace sampling almost always reduce noise and artefacts.
>     count 350 999 // Should reduce those dark splotches.
>   // Second value set a sampling direction pool.
>   // Second value MUST be greater than the first
>     recursion_limit 2 // 1 may even be enough.
>     nearest_count 20 5 // enable adaptive sampling and pretrace
>   // second value must be the smaller one.
>   // Larger first value often help to reduce the dark splotches,
>   // and also make then less sharp.
>     error_bound 0.35
>    }
>   #end
> }
> 
> Try raising the oscilloscope a little bit above the table. After all, 
> most have rubber pads under them acting as short legs.

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