In article <3fecaa85$1@news.povray.org>, gitran_nospam_@wanadoo.fr 
says...

> news:MPG.1a56abe37b4346cb98968d@news.povray.org...
> > Most of the spacecraft now looks rather dark, even after I
> > added several secondary lightsources. Any suggestions ?
> 
> In addition to what Hugo said:
> 
> You need to define your lighting set-up: is it solar light only or a
> combination or solar light and planetary radiance? Don't forget that lights
> can be > 1 and in fact it's rather recommended in this sort of scene if you
> want to have sharp contrasts. Radiosity can help a lot there. I did once a
> rendering of the ISS that way
> (http://www.oyonale.com/iss/english/museum_08.htm), The model isn't mine and
> the pic could be much better (just to a few hours to set up, it was mostly a

> for altitude and earth size. I based it on reference images for the
> materials but didn't try too hard (I should have coded the model myself for
> that).
> 
> And do you want it to be pretty (sci-fi like, with lots of secondary lights,
> even if they do not make sense in deep space) or just realistic (all parts
> not lit by the sun or a planet should be black) ? Artistic renderings of
> spacecraft are rarely realistic in terms of lighting: see
> http://icb.nasa.gov/cassini.gif : most of the light comes right from the
> artist's mind...

To reply to what Hugo and Gilles said:

I have been using lots of images of the spacecraft from 
http://saturn.jpl.nasa.gov/multimedia/images/spacecraft/index.cfm as a 
reference, plus Wavefront obj files (polygon meshes) from 
http://samadhi.jpl.nasa.gov/models/ which includes no useful texture 
info but highly useful 'geometric' info. I suspect many of the metallic 
parts are aluminum.

Here are two renderings made using the metals.inc file supplied with 
POV:

http://www.mmedia.is/~bjj/povstuff/spacecraft/cassini_69_bright.png
http://www.mmedia.is/~bjj/povstuff/spacecraft/cassini_70_bright.png

These are much more recent versions than the ones on the webpage at my 
site in case anyone has looked at them (I plan to replace them Real Soon 
Now). Only one lightsource is used. In particular, the flat area below 
the big antenna disc look unrealistic, it should be largely in shadow. 
Closeup renderings can become especially unrealistic using these metals. 
The model is extremely (and probably ludicrously !) detailed so nice 
closeups should be possible.

Here are the same renderings done using a modified metals.inc where the 
ambient component is almost 0. In addition I'm using two secondary 
lightsources, both of intensity <1,1,1>/2 and I'm ware that the lights 
can have an intensity >1.

http://www.mmedia.is/~bjj/povstuff/spacecraft/cassini_69.png
http://www.mmedia.is/~bjj/povstuff/spacecraft/cassini_70.png

The area below the anteanna disc is much more realistic. However, the 
magnetometer boom (the big, golden boom) is almost invisible. Also the 
Huygens probe (the big, 'circular', golden object attached to Cassini's 
side) looks very dark. This can be compared to this photo showing 
Huygens being attached to Cassini:

http://www-pao.ksc.nasa.gov/kscpao/images/large/97pc1098.jpg

Overall the renderings using the modified metals.inc look better to me 
but I'm not completely happy. One additional problem is that the photos 
I have of the spacecraft are all taken inside a well lit room where the 
bright walls get reflected from the spacecraft.

I plan to make mainly sci-fi like renderings with several secondary 
lights.

-- 
Bjorn Jonsson / bjj### [at] ZZZmmediais
Address changed to avoid spam. Remove YYY and ZZZ to reply.
http://www.mmedia.is/~bjj

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