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 CAD / Ray-Tracing / 1612
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Subject: 
Re: Sand Green and POV
Newsgroups: 
lugnet.cad, lugnet.inst, lugnet.cad.ray
Date: 
Mon, 20 Jan 2003 19:51:30 GMT
Viewed: 
35 times
  
"Kevin Clague" <kevin_clague@yahoo.com> wrote in message
news:H90qHs.CCn@lugnet.com...
Mike,

  In the first image, there are no shadows.  What you see are reflections.

I suspected as much when I really started to look at it after you noted that
you were using a shadowless light source.


[ ... snipped ... ]


  Ambient light comes from *all* directions, and therefore creates no
shading.  Diffuse light comes from a specific point, and therefore can
produce shading and shadows.  In POV-Ray, diffuse means the shading part • of
rendering and is controlled in the surface description of the model (it is
packed into the Color definitions by L3P.)  Shadows on the other hand are
defined by the light sources themselves.

  LPub automatically turns off shadows in building instruction images
(whether you want them or not (do I feel another option control request
brewing?)).  The default settings for ambient and diffuse used by L3P are
0.4 for ambient and 0.4 for diffuse.  In my previous experience with
lighting models, it was my understanding that it was desired to have • ambient
+ diffuse + reflection equal to 1, so when I turned off reflections, I
modified ambient and diffuse so they totaled one.

  Back to my pistons that were too dark on the underside....  I realized
that the undersides were darker than the tops because the diffuse light • was
lighting the top, but not the bottom.  To reduce this brightness • difference,
I increased the ambient levels, and decreased the diffuse levels, but made
sure they added up to 1.

  For sport you can try two extremes:  ambient 1.0, diffuse 0 (which will
give you shading less images like LEGO uses), or ambient 0 and diffuse 1
(which makes any unlighted surface black.  There are those that render
building instructions with only ambient (before the ambient controls, they
used the POV-Ray quality settings to make this happen.)

  LPub/L3P lets you define how many light sources you want and what their
placements are, and those lights are used when creating building
instructions. So if you want a different lighting configuration than what
L3P defaults to, you can set that up in the L3P->Lights tab of LPub's
configuration controls.

This is really useful.  I need to sit down with a less complex model and run
through all of the various settings.


  On the topic of patience, I feel the same way.  I'm new to building
instructions, and you and Steve Barile have been at it a while.  Thanks • for
your patience and input on how to make LPub better suite your needs.  I'm
enjoying the synergy that is happening on the topic of building • instructions.

Kevin

Happy to provide input and I appreciate your interacting with the community
so openly.

Mike


--
Mike Walsh - mike_walsh at mindspring.com
http://www.ncltc.cc - North Carolina LEGO Train Club
http://www.carolinatrainbuilders.com - Carolina Train Builders
http://www.bricklink.com/store.asp?p=mpw - CTB/Brick Depot



Message is in Reply To:
  Re: Sand Green and POV
 
Mike, In the first image, there are no shadows. What you see are reflections. The reflection of the smoke stack on the top of the engine compartment looks like a shadow because the smoke stack is darker than the abient light you see other places. (...) (22 years ago, 20-Jan-03, to lugnet.cad, lugnet.inst, lugnet.cad.ray)

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