POV-Ray : Newsgroups : povray.binaries.images : Moving indoors : Re: Moving indoors Server Time
18 Oct 2021 22:11:22 EDT (-0400)
  Re: Moving indoors  
From: Cousin Ricky
Date: 16 Aug 2021 16:28:54
Message: <611aca86$1@news.povray.org>
On 2021-08-16 12:58 PM (-4), Chris R wrote:
> 
> This was my first crack at updating the scene to use fresnel reflections.  I'm
> not entirely happy with it, so I am rerunning with some different min/max
> reflection values for the pool table.  I noticed the highlights on the table
> from the ceiling lights seem more pronounced now, but I'm not sure if I like
> them that way.

What value are you using for reflection?  It should be reflection { 1
fresnel } conserve_energy for the picture window, and close to 1 for the
balls and table, unless you want reduced gloss.

What value are you using for phong/specular?  At full gloss with an IOR
of 1.5, Fresnel reflection varies from 0.04 to 1.00, depending upon
angle of reflection.  I find that a value of specular albedo 0.05
normally works well; you can use this on the balls.  However, with much
of the table at a shallow reflection angle--85 degrees, I'm
guessing--reflection is around 0.6.  Try specular albedo 0.6 or phong
albedo 0.6 on the table, since the highlights are mostly on the top; but
if you still get strong highlights on the side of the table, you may
have to use an aoi texture with two different phong or specular values.
For the picture window, of course, you would use the minimum 0.04.

Always use the albedo keyword with phong and specular, so you can easily
align your highlight level with the reflection level, and not have to
worry about tweaking the highlights every time you change phong_size or
roughness.

The layered texture trick I posted above simulates the 3.8 improvements
in Fresnel reflection on opaque objects.  If you use this trick, use it
only for the balls and the table; do not use it for the picture window.

If you want only half gloss on the balls or table, reduce the highlight
by half, for example:

  #version 3.7;
  finish
  { reflection { 0.5 fresnel } conserve_energy
    specular albedo 0.025 // texture for balls and side of table
    specular albedo 0.3 // texture for top of table
  }

Things get much easier with POV-Ray 3.8, no layered textures necessary:

  #version 3.8;
  finish
  { fresnel 1
    reflection { 1 } conserve energy
    specular albedo 1 // works for balls, table, and window!
  }

Or, for half gloss:

  #version 3.8;
  finish
  { fresnel 0.5
    reflection { 0.5 } conserve energy
    specular albedo 0.5 // works for balls and table
  }


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