POV-Ray : Newsgroups : povray.general : Lighting Artifacts Help ? : Re: Lighting Artifacts Help ? Server Time
22 Feb 2024 00:20:37 EST (-0500)
  Re: Lighting Artifacts Help ?  
From: scottb613
Date: 19 Jan 2022 10:50:00
Message: <web.61e832e5884f25c2718d9114df363ea7@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:

> > Alain Martel <kua### [at] videotronca> wrote:
>
> >> 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.
>
> Attachments are not allowed in this group. You can only have attachments
> in the groups that have .binaries. in their names.
> For scene files as zip files, you want to use povray.binaries.scene-files
> For shorter scene files, you can use povray.text.scene-files
> For images, you want to use povray.binaries.images
>
> >
> > 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
> >
> >
>
> Unless your scene contains reflective surfaces or transparent objects
> with an ior, you don't need the photons block.
> Not an issue. If there are no object with a photons block that set it as
> a target, then, there will be no photons shooting.
>
> You want to reduce pretrace_end. The default value that you use is to
> large when the resolution is larger than 800 by 600.
> Good value can be 0.01 down to 0.0025. In larger renders, it may be
> preferable to go even lower.
>
> You probably don't need a count of 1600. You could probably reduce that
> to 400 to 500.
>
> As this is an exterior scene, a recursion_limit of 1 is probably enough.
> In some cases, a value of 2 may be needed. 3 is overkill.
>
> You may want to reduce low_error_factor to something in the 0.2 to 0.3
> range.
>
> You very probably need to reduce minimum_reuse. You may need to reduce
> it down to 0.005. Just make it slightly smaller that your pretrace_end.
>
> brightness should remain at it's default value of 1. Better not use it
> at all.
>
> You probably don't need to set adc_bailout and use the default value.
>
> error_bound could benefit from a smaller value. Values of 1 ti 1.8 are
> OK when using regular lights as your main illumination. You usually need
> it to be less than 0.5 when you use emissive object(s) as light sources.
>
>
> Note about the photons block for the light_source. That block is never
> needed UNLESS you want to prevent that light from shooting photons.
> All non-shadowless lights always shoot photons at all target objects in
> any photons scene.
> That block was required way back in version 3.3. It's no longer needed
> since version 3.5.
> Now, the block :
>    photons { refraction on reflection on }
> is the default for all lights *unless* they are shadowless.
>
> When using fading lights, it's better to set fade_distance to 1 and
> increase the light's intensity as needed.
>
> light_source{ <25, 20, 45> // create directly at the desired location
>  rgb 121 // color keyword is never needed when rgb is used
>   // float value get promoted to a full rgb vector
>   // the intensity is not limited to the 0..1 range
>   // it can get larger than 10 000 000
>  fade_distance 1
>  fade_power 2
>  }
>
> Fading lights often don't play well with the shadowless attribute.
> shadowless lights never cause any highlight and never shoot any photon.
> Most of the time, you don't need them.
> They may cause some issue when used in a radiosity scene.

Hi Alain,

Thanks so very much for detailed response - greatly appreciated.

I did try scaling the shapes to x10 as you suggested and it was a big
improvement.

You've given me plenty to think about and try - I'll be referring back to this
as I try your other suggested changes. Perhaps it's time to delve a bit deeper
and get out of my comfort zone.

Have a good day.

Regards,
Scott


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