Content-Transfer-Encoding: 8Bit



Hi,



I played around a bit with photons and I wonder why the following picture

does not contain any (colored) rays from the diamond into the media.



The color dispersion in this images seems to contain just a few colors and

no smooth color transitions.



Does someone know what causes these effects and how to make it look more 

realistic?



Thank You,



Hans



P.S.:

Yes, I know, it looks terrible...

Post a reply to this message

Attachments:
Download 'us-ascii' (100 KB) Download 'us-ascii' (2 KB)

Johann Uhrmann <juh### [at] fh-landshutde> wrote in
news:3d54588c@news.povray.org 

> --nextPart1312712.W6geO5KgaW
> Content-Transfer-Encoding: base64
> 
> Content-Disposition: attachment; filename="photon.jpg"
> 
> 
> 
> /9j/4AAQSkZJRgABAQEASABIAAD//gAXQ3JlYXRlZCB3aXRoIFRoZSBHSU1Q/9sAQwABAQE
> BAQEB 
> 
> AQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQE


something is wrong with this attachment


-- 
#macro g(U,V)(.4*abs(sin(9*sqrt(pow(x-U,2)+pow(y-V,2))))*pow(1-min(1,(sqrt(
pow(x-U,2)+pow(y-V,2))*.3)),2)+.9)#end#macro p(c)#if(c>1)#local l=mod(c,100
);g(2*div(l,10)-8,2*mod(l,10)-8)*p(div(c,100))#else 1#end#end light_source{
y 2}sphere{z*20 9pigment{function{p(26252423)*p(36455644)*p(66656463)}}}//M

Post a reply to this message

"Johann Uhrmann" <juh### [at] fh-landshutde> wrote in message
news:3d54588c@news.povray.org...
>
> I played around a bit with photons and I wonder why the following picture
> does not contain any (colored) rays from the diamond into the media.
>
> The color dispersion in this images seems to contain just a few colors and
> no smooth color transitions.

Hi there Johann,

Same as 'Raf256', I couldn't see your attached image (maybe that "8-bit"
encoding?). Might have been better to post each part at their respective
places here at the newsgroups, namely image file here, pov file to
povray.text.scene-files (the text in message). Regardless....

....I rendered your script and puzzled over it a while. Found that I could
not get photons in the media other than from the spotlight. When I made a
box to act as media container and room the reflecting photons showed up in
the media, not when only open air media was used.

The photon mapping was working okay showing on the ground, just not in
media, before making that change. I did need to increase the light source
color above one to see it good enough. If the transmit 0.95 is changed to
1.2 that also brightens it up but probably not always okay to do that.

I really wonder about that problem of the missing photons in media if it
isn't enclosed, something either not right or I missed a reason for it. I
won't say it's a bug unless others find likewise.

Now, about that dispersion. Reason that looked sharp-edged for you I guess
is because the default of 7 colors was used, so adding a dispersion_samples
14 would double that.

About that media again. I was surprised to find how the box container
addition slowed it down terribly. I couldn't seem to speed it back up to
it's original render-time, maybe something to do with the previously missing
media photons and now it shows all bouncing around from reflection and
refraction. Still was much, much slower than I'd have expected. So slow in
fact I quit trying to check on it.

Only half helpful perhaps.

Post a reply to this message

"hughes b" <omn### [at] charternet> wrote in
news:3d55839d@news.povray.org 

> Hi there Johann,
> Same as 'Raf256'

thanks ;)

>  I couldn't see your attached image (maybe that
> "8-bit" encoding?). Might have been better to post each part at their
> respective places here at the newsgroups, namely image file here, pov
> file to povray.text.scene-files (the text in message). Regardless....

try (in Xnews it works)
no content-transfer-encoding selected
no Conntent-type selected 
Mime-Version 1.0
Attachments : Use MIME - ye


-- 
#macro g(U,V)(.4*abs(sin(9*sqrt(pow(x-U,2)+pow(y-V,2))))*pow(1-min(1,(sqrt(
pow(x-U,2)+pow(y-V,2))*.3)),2)+.9)#end#macro p(c)#if(c>1)#local l=mod(c,100
);g(2*div(l,10)-8,2*mod(l,10)-8)*p(div(c,100))#else 1#end#end light_source{
y 2}sphere{z*20 9pigment{function{p(26252423)*p(36455644)*p(66656463)}}}//M

Post a reply to this message

hughes b wrote:

> Hi there Johann,
> 
> Same as 'Raf256', I couldn't see your attached image (maybe that "8-bit"
> encoding?). 

Well, sorry for that unreadable attachment. I switched 8-bit-encoding off - 
hope this will fix it.

> [...]
> I really wonder about that problem of the missing photons in media if it
> isn't enclosed, something either not right or I missed a reason for it. I
> won't say it's a bug unless others find likewise.

Maybe this problem is from the same type as those "no laser effect"-threads 
I just discovered.

> Now, about that dispersion. Reason that looked sharp-edged for you I guess
> is because the default of 7 colors was used, so adding a
> dispersion_samples 14 would double that.

Thanks for that hint :)

> About that media again. I was surprised to find how the box container
> addition slowed it down terribly. I couldn't seem to speed it back up to
> it's original render-time, maybe something to do with the previously
> missing media photons and now it shows all bouncing around from reflection
> and refraction. Still was much, much slower than I'd have expected. So
> slow in fact I quit trying to check on it.

I guess, I will try it anyway. Using a linux-cluster should speed it up a 
bit. 
Speaking of clusters: Currently, I am using shell scripts to distribute the 
load. Unfortunately, this does not speed up the photon map creation. Has 
someone an idea how to parallelize photon maps?

> Only half helpful perhaps.

It was all the help I hoped for ;)


Thank You,

Hans

Post a reply to this message