POV-Ray : Newsgroups : povray.general : Lighting Artifacts Help ? : Re: Lighting Artifacts Help ? Server Time
21 Feb 2024 22:13:15 EST (-0500)
  Re: Lighting Artifacts Help ?  
From: scottb613
Date: 18 Jan 2022 11:45:00
Message: <web.61e6ed71884f25c2718d9114df363ea7@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:
> > Hi Folks,
> >
> > Been using POVray for years - mainly just to showcase my model work - I'm
> > certainly not an expert.
> >
> > I'm using the latest POVray.
> >
> > Any ideas - why I'm getting the strange lighting artifacts along the centerline
> > of the boiler?
> >
> > Any other suggestions to improve the image - I'd greatly appreciate.
> >
> >
> > Image on Flickr
> > https://flic.kr/p/2mXWyTd
> >
> >
> > Regards,
> > Scott
> >
> >
> >
> >
> >
> >
> Those may be some radiosity artifacts.
> What are your radiosity settings, if any ?
>
> Some times, scaling up everything by 10 can make those disappear, or
> make them smaller. In that case, it indicate rounding errors.

Hi Alain,

Thanks so much for the response.

Hmm - I tried to post my POV file as a zipped attachment - I selected it but it
doesn't appear to upload it anywhere. Did same on this message.

Here is the "Lighting" block I used in the images - it's probably not correct -
I just played with values until I got something that seemed to work - LOL - much
like a chimp writing a symphony.

###################################################################################

"// adding a photon{} block to global_settings activates photon mapping.
// photons also need to be adjusted for light sources and objects.
global_settings {
  photons {
    spacing 0.01                 // specify the density of photons
    //count 100000               // alternatively use a total number of photons

    //gather min, max            // amount of photons gathered during render
[20, 100]
    //media max_steps [,factor]  // media photons
    //jitter 1.0                 // jitter phor photon rays
    //max_trace_level 5          // optional separate max_trace_level
    //adc_bailout 1/255          // see global adc_bailout
    //save_file "filename"       // save photons to file
    //load_file "filename"       // load photons from file
    //autostop 0                 // photon autostop option
    //radius 10                  // manually specified search radius
    // (---Adaptive Search Radius---)
    //steps 1
    //expand_thresholds 0.2, 40
  }
}

#default{ finish{ ambient 0 diffuse 1 }}

// radiosity (global illumination) settings
global_settings {
  radiosity {
    pretrace_start 0.08           // start pretrace at this size
    pretrace_end   0.04           // end pretrace at this size
    count 1600                     // higher -> higher quality (1..1600) [35]
    nearest_count 10              // higher -> higher quality (1..10) [5]
    error_bound 1.0               // higher -> smoother, less accurate [1.8]
    recursion_limit 3             // how much interreflections are calculated
(1..5+) [3]
    low_error_factor .5           // reduce error_bound during last pretrace
step
    gray_threshold 0.0            // increase for weakening colors (0..1) [0]
    minimum_reuse 0.015           // reuse of old radiosity samples [0.015]
    brightness 0.5                 // brightness of radiosity effects (0..1) [1]

    adc_bailout 0.01/2
    //normal on                   // take surface normals into account [off]
    //media on                    // take media into account [off]
    //save_file "file_name"       // save radiosity data
    //load_file "file_name"       // load saved radiosity data
    //always_sample off           // turn sampling in final trace off [on]
    //max_sample 1.0              // maximum brightness of samples
  }
}




// Persistence of Vision Ray Tracer Scene Description File
// File: ?.pov
// Vers: 3.6
// Desc: Basic Scene Example
// Date: mm/dd/yy
// Auth: ?
//

#version 3.6;

#include "colors.inc"

global_settings {
  assumed_gamma 3.0
}



// ----------------------------------------

light_source {
  <200,50,150>       // light's position
  color rgb 1.3       // light's color
  photons {           // photon block for a light source
    refraction on
    reflection on
  }
}



// ----------------------------------------

// ----------------------------------------

light_source {
  <-200,-50,250>       // light's position
  color rgb 1.3       // light's color
  photons {           // photon block for a light source
    refraction on
    reflection on
  }
}

// create a regular point light source
light_source {
  0*x                  // light's position (translated below)
  color rgb <1,1,1>    // light's color
  translate <25, 20, -45>
  // light_source { ...
  // put this inside a light_source to add light fading
  fade_distance 12
  fade_power 2
  shadowless

}

// create a regular point light source
light_source {
  0*x                  // light's position (translated below)
  color rgb <1,1,1>    // light's color
  translate <25, 20, 45>
  // light_source { ...
  // put this inside a light_source to add light fading
  fade_distance 11
  fade_power 2
  shadowless

}"

Regards,
Scott


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