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 CAD / Ray-Tracing / 1853
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Subject: 
Re: Can anyone help by suggesting some lighting tips?
Newsgroups: 
lugnet.cad.ray
Date: 
Tue, 1 Jul 2003 01:26:00 GMT
Viewed: 
1725 times
  
In lugnet.cad.ray, Anders Isaksson wrote:
Allan Bedford wrote:

As you will probably see, I was really just shooting in the dark
(pardon the pun) when it came to using the lights.  I would welcome
any thoughts and/or suggestions.  I've tried searching the POV-Ray
site, but couldn't find something as simple as, "here's how to
position a single sample light, to give you a simple sample render."


(I don't know how much of this you can affect from LPub)

I'm quite happy/comfortable editing the .pov file directly... it's just the
values and directions I'm still trying to get a grip on.

One way is to add a 'light.dat' to your model at a position you want the
light to come from. Not to close though...

Is this different than some of the .inc files that others have already suggested
using?  And if so, can you point me to some further info or an example?

I usually put the lights far, far away from the model, to get more of the
surroundings lighted (more like sunshine).

This is something I was thinking of... for pretty much the same reasons.  I just
can't find the mix of values that works right.  I seem to be either much too
dark, or way too bright.

In a pov file with the default lights generated by L3P I locate the
'light_source' at the end of the file, and multiply all values by 10 (throw
the decimals at the same time, they're unnecessary).

I can try this.  My values (presumably) are coming from LPub, through L3P, then
into POV-Ray.  I have no idea what I'm really starting off with.

I also usually set all lights, execept one, as 'shadowless', to get away
from the 'three spot lights' look. Quick rendering at a small size, 'QUAL=0'
is used to decide which light should cast a shadow.

This is exactly what I want.  (although sometimes I actually want completely
shadowless).  I'm not fond of the 3 shadow effect, as I find it looks quite
wrong.  Even in artificial studio lighting, you don't see so many conflicting
shadows.  I really want a natural look.  (which is ironic, since these are
computer-generated bricks rendered in a computer lit world).

Also, it is often good to add an extra (shadowless) light at exactly the
same point as the camera, as this will make sure everything you see is
lighted one way or another - this brings out the details when you look
_into_ the model from the camera. You may have to give this light a lower
intensity:

light_source {
<-320,-898,-41>
color rgb 0.4 * <1,1,1>
  shadowless
}

I will try this!

I notice that although I feed LPub one set of camera parameters, those don't
seem to be what ends up getting used by POV-Ray.  I have been using 5, 30 as my
latitude and longitude.  But these values seem to be translated by the time they
get to POV-Ray.  Which makes it hard to figure out where to add my lights.  Is
that making sense?  Or am I the only one struggling with this?

Remember: if you add many lights, lower their intensity, so that the total
light is between 1 and 3 (or thereabout...)

Yes, figured that one out the hard way.  :)

(Still talking about L3P generated files)

I also almost always move the camera away tenfold (or more) from the model,
and change the 'angle' parameter to still have a reasonable size of the
model. This gives a more realistic perspective (IMO).

I was wondering about that too.  The perspective that is getting generated
(LPub>L3P>POV) seems quite exagerated.  When you say the 'angle' parameter, do
you mean the camera angle/direction?

In my Brickshelf gallery you can see some renderings I made long before the
'radiosity craze' (sorry, I don't have the URL, and am not online while
writing, so I can't give you any link. Search for 'sinking ships' or my
name).

I'll do that!  Thanks!  I'm offline at the moment too, so I'll respond later to
this particular part.

Thanks very much for your input.

Best regards,
Allan B.



Message has 1 Reply:
  Re: Can anyone help by suggesting some lighting tips?
 
"Allan Bedford" <ExpertBuilder-DELET...otome.com> skrev i meddelandet news:HHBnzC.uH@lugnet.com... (...) suggested (...) Sorry, I have never used it, just read about it. It is supposed to place a light at exactly at the spot where you put that piece (...) (21 years ago, 1-Jul-03, to lugnet.cad.ray)

Message is in Reply To:
  Re: Can anyone help by suggesting some lighting tips?
 
(...) (I don't know how much of this you can affect from LPub) One way is to add a 'light.dat' to your model at a position you want the light to come from. Not to close though... I usually put the lights far, far away from the model, to get more of (...) (21 years ago, 30-Jun-03, to lugnet.cad.ray)

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