Hi!

I am posting two images, one with radiosity, a point light source, and a
blue sky...other one rendered using hdri map in mlpov without any
conventional light source. After seeing some wonderful images with hdri, I
should say I am a little disappointed with the result....the render with
conventional lighting looks far better. I guess I have used some
inappropriate radiosity parameters. Can anybody please throw some light on
how to improve the image. I am giving the radiosity settings for both the
images.
radiosity setting for conventional lighting:
radiosity {
      pretrace_start 0.08
      pretrace_end   0.04
      count 35

      nearest_count 5
      error_bound 1.8
      recursion_limit 3

      low_error_factor 0.5
      gray_threshold 0.0
      minimum_reuse 0.015
      brightness 1

      adc_bailout 0.01/2
    }

radiosity for hdri
radiosity {
    pretrace_start 0.08           // start pretrace at this size
//To be used with HDRI maps
    pretrace_end   0.04           // end pretrace at this size
    count 50                      // higher -> higher quality (1..1600) [35]
    nearest_count 5               // higher -> higher quality (1..10) [5]
    error_bound 1.8               // 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 1                  // brightness of radiosity effects (0..1)
[1]

    adc_bailout 0.01/2
    normal on                     // take surface normals into account [off]
  }

thanks
sup


"Skip Talbot" <sta### [at] uiucedu> wrote in message
news:3f84d8d7$1@news.povray.org...
> HDRI stands for High Dynamic Range Imaging.  Its basically an image format
> that doesn't have a limit to the brightness levels of the colors.  Mael
> wrote a patched a version of POV 3.5 that reads such a format for use in
> scenes.  Download his patch here:
> http://pov.monde.free.fr/mael/mlpov083.html
> English older version instructions:
> http://martial.rameaux.free.fr/mael/mlpov081eng.html
>
> Run some of the sample scenes to see what it can do and for the syntax.
> There were several posts on this board a few months ago that demo what
HDRI
> can do.  Here's an aircraft I rendered using an HDRI map:
> http://members.aol.com/skipt1/3d/highres/longez6.png
>
> Skip
>
>

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Attachments:
Download 'b747_jal_old-radlow.jpg' (166 KB) Download 'b747_jal_old_hdri1.jpg' (107 KB)

Preview of image 'b747_jal_old-radlow.jpg'

Preview of image 'b747_jal_old_hdri1.jpg'

What's wrong with your HDRI rendering?  It looks good to me.  But seriously
folks... It appears that maybe you have rotated the HDRI sphere so that the
bright spots are underneath your plain (and plane).  That means the only
thing illuminating your scene is the rather dull floor.  Make sure the up on
the HDRI is aligned with the normal of your plane.

You're not going to get well defined shadows with HDRI so I like to back the
shadows up with a dim point light or area light (if you've got the computer
for it).  Try adding one aligned with the bright spots on the HDRI so that
illumination lines up and make it real dim so the scene doesn't wash out.

Radiosity is all about tweaking and more tweaking.  Try these radiosity
values for some higher quality but a slower redner, and play with the
assumed gamma in your global settings to give the image some contrast.

global_settings {
  assumed_gamma 2.0
  radiosity {
    pretrace_start 0.08
    pretrace_end  0.01
    count 1600
    nearest_count 10
    error_bound 0.5
    recursion_limit 1
    low_error_factor .25
    gray_threshold 0.0
    minimum_reuse 0.015
    brightness 1
    adc_bailout 0.01/2
  }
}

Skip

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