POV-Ray : Newsgroups : povray.newusers : Background and area light : Re: Background and area light Server Time
1 Jul 2022 19:37:22 EDT (-0400)
  Re: Background and area light  
From: Alain
Date: 30 Dec 2016 14:42:56
Message: <5866b8c0@news.povray.org>

> I'm trying to render a long rectangle (with some extra stuff) using an area
> light. The problem is that I always see a dark background, even if I extend the
> area light further along the z direction. If I change the perspective, I also
> see that extending the area light region does not have much effect, there is
> always a darker side on the rectangle, which I don't know why. I've also tried
> increasing the height (y direction) of the area light with a better result,
> however the shadows are smaller in that case.
>
> What I want is to make most of the floor and background as white as possible but
> without making the rectangle to look too bright (that's why I use a gray
> background).
>
> The code is here (I'm using the rc3metal files; btw, is there a way to make the
> Bronze rectangles even more realistic? do I need a turbulence or something like
> that?) :
>
>
> # -----------------------------------------------------------------------------
>
> #include "colors.inc"
> #include "textures.inc"
Not used
> #include "metals.inc"
Not used
> #include "rad_def.inc"
Not used
> #include "rc3metal.inc"
> // RC3Metal_Set_highlight (0.3)
> #declare BLURRED_REFLECTION = 1;
>
> global_settings
> { assumed_gamma 1
>   max_trace_level 30
This may need to be increased.
>     radiosity
>     { count 200
Try something like count 200 25000
It can really improve your results.
>       error_bound 0.1
>       normal on
You can probably do without this
>       pretrace_end 0.005
>       recursion_limit 6
Maybe a little large, 3 or 4 should be enough.
>       brightness 0.5
If it's to dim, try removing this.
>     }
> }
>
> background { color rgb <0.6, 0.6, 0.6> }
>
> camera{
>     location <100, 50, -30>
>     look_at <15, -40, 110>
>     up        1 * y
>     right     2 * x
> }
>
> #for (z_disp, 22, 260, 44)
>     box {
>         <0, 0, z_disp>, <40, 10, z_disp + 22>
>         RC3Metal_Texture (RC3M_C_CHROME, 0.3, 0.3)
>         // normal {granite 0.1
>   // scale <0.1, 20, 1>
>   // no_bump_scale}
>     }
> #end
>
> #for (z_disp, 0, 260, 44)
>     box {
>         <0, 0, z_disp>, <40, 10, z_disp + 22>
>         RC3Metal_Blur_t
>         ( RC3Metal_Texture (RC3M_C_ZINC, 0.5, 0.7),
>         0.25, 0.001, 1
>         )
>     }
> #end
>
> #for (z_disp, 18, 260, 44)
>     box {
>         <0, 10, z_disp>, <40, 12, z_disp + 30>
>         RC3Metal_Texture (RC3M_C_BRONZE_NEW, 0.2, 0.2)
>         // normal {granite 0.1
>   // scale <0.1, 20, 1>
>   // no_bump_scale}
>     }
> #end
>
> plane {
>     // We can use 'y' instead '<0, 1, 0>'
>     <0, 1, 0>, 0
>     texture {
>         // pigment { checker color White color Black }
>         pigment{ color White }
Try using some pattern instead, like granite or bumps. To get lighter 
general tints, use a colour_map:
colour_map{[0 rgb 0.6][1 rgb 1]}
To get some special effects:
colour_map{[0 rgb 0.6][0.98 rgb 0.97][1 rgb 10]}
>         finish{ambient 0 diffuse 0.8}
>         // normal {granite 0.5 scale 0.001}
>     }
> }
>
> light_source { <-30, 150, 10>
>                color White
>                area_light 80*x, 300*z, 17, 33
>                jitter
	area_illumination // spread the illumination
	adaptive 0 // offer dramatic speed improvment
>                }
>
> # -----------------------------------------------------------------------------
>
>
>


still act as a point light whenever shadows are not concerned.

To look realistic, metallic textures need something to reflect other 
than a plain background.
Use a sky_sphere with some clouds or a high dynamic range light probe. 
You may also use a plane as a kind of sky or a very large sphere. It can 
also be some objects that don't need to be complex. Some boxes and 
spheres with non-uniform and non-metallic textures can do the trick.


your metal texture rely essentially on actual reflection rather than 
radiosity.



Alain


Post a reply to this message

Copyright 2003-2021 Persistence of Vision Raytracer Pty. Ltd.