On 25/10/2017 22:14, Alain wrote:
> Le 17-10-25 à 14:57, Stephen a écrit :
>> On 25/10/2017 17:31, Bald Eagle wrote:
>>> "cbpypov" <nomail@nomail> wrote:
>>>> Hi,
>>>>
>>>> I'm trying to render a high quality "cover art" for a physics thesis
>>>> (nanophotonics). I have basically two questions:
>>>>
>>>>    1. What is the best way to generate a "glowing field distribution"?
>>>>    2. What is the best way to illustrate a light ray or "photon 
>>>> path" coming from
>>>> an emitter, say a small glowing sphere
>>>
>>> I would say that you should look at Paul Nylander's work
>>> http://www.bugman123.com/index.html
>>> as he's and engineer, and has done an awful lot of very professional 
>>> quality
>>> scientific visualization with POV-Ray.
>>>
>>>> For 1): Say I have field values in 3D that I could assign to desired 
>>>> colors and
>>>> brightness values. So that that I have e.g. a list of (x, y, z, R, 
>>>> G, B,
>>>> brightness).
>>> .....
>>>> So how can I achieve something like
>>>> this?
>>>
>>> You use an EMISSIVE media.
>>> I'd also consider generating your field as a df3 file, and then you 
>>> can "sculpt"
>>> the media density with that df3 information.
>>>
>>
>> DF3s are probably the way to do it. One drawback is that PovRay uses 
>> df3s as a monochrome input. So you would need three of them to R G & B 
>> images. jr might be able to help you with the df3 format as he is 
>> working on a set of df3 utilities.
>>
>> The code I use for rendering in colour with df3s is:
>>
>>          #declare PF = 64  ; // multiplication factor
>>
>>      #declare Df3_Material0 =
>>      material{
>>        texture {
>>          pigment {
>>            colour rgbft <1.000,1.000,1.00,0.000,1.000>
>>          }
>>
>>        }
>>
>>        interior{
>>          //ior                 1.000
>>          //caustics            0.000
>>          //dispersion          1.000
>>          //dispersion_samples  7.000
>>          //fade_power          0.000
>>          //fade_distance       0.000
>>          //fade_color          rgb <0.000,0.000,0.000>
> Those can, and should, be omited.

No chance. I use a modeller and that is what it outputs
But it is good that you mention it.

>>          media {
>>            method     3
>>            // intervals  10
> MUST stay at 1. Don't use intervals is best.
> 

Holes in the brain. I keep getting this the wrong way round. :-(


>>            //samples    1, 1
> // May be omited : Use 10 samples by default
> // Second value NOT used.
>>            //confidence 0.900
>>            //variance   0.008
>>            //ratio      0.900
> // All 3 NOT used with method 3
>>            absorption rgb <0.000,0.000,0.000>
>>            emission   rgb <1.000,0.000,0.000>     * PF
>>            aa_threshold 0.050
>>            aa_level    4
>>            density {
>>              density_file df3 "Your_red.df3"
>>              interpolate 2
>>            }
>>
>>          }
>> By default, method 3 use only 1 interval and 10 samples.
> Using more that a single intervals will dramatically increase the time 
> required by your render.
> If you need more sampling, simply increase the samples vlue.
> As only a single interval is used, only the first samples value is ever 
> used. A second valus, if present, is silently ignored.
> Also, confidence, variance and ratio, are used to distribute samples 
> within various intervals, they are not used, and silently ignored.
> 
> intervals 1 samples 500
> is much faster than
> intervals 10 samples 5
> for 10 times as many samples.

I wonder how many times I will need to be told. I seem to have a blind 
spot for this. I hope you don't get bored easily. ;-)

But I should not post bad information.



-- 

Regards
     Stephen

Post a reply to this message