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Scene Size vs Lighting

Posted: Sat Oct 05, 2019 2:42 am
by SGR FA
Hi there,

I'm new to the forum so first of all: Thanks for this wonderful software and its community support !

It may be obvious but unfortunately I did not find why, apparently, envmap lighting may change regarding scene size (bounding box based ?): for example if we add an airplane far away from a building (or if we add a huge flat surface on the floor), we don't get same results : shadows are more/less sharp, specular gloss can be less/more wide, rooms interiors are less/more bright...

I found this interesting topic :

viewtopic.php?f=5&t=11183&p=111427&hili ... ng#p110664

but I don't get if there is any existing param/tip to define an expected horizon distance and its possible effects on gain or emission scale (and rendering time). Maybe we have to use a trick to produce images for our scenario comparisons.

Any help would be greatly appreciated.

Best Regards.

Re: Scene Size vs Lighting

Posted: Sat Oct 05, 2019 11:20 pm
by Paraket
Hello!

I did not notice such effects when working in 3ds max in centimeters. Check Display unit scale and system unit scale.

You can change the blurring and intensity of the shadows using the “Quadratic (a)” parameter (the optimal range of values is 0.01-0.035). The scene will turn yellow the higher the value. It can be easily fixed by changing the White point preset (the blue ones are A, D50, F2 and F11).
You can get a similar effect by changing the gamma value of the HDR card, but this is not available from 3ds max.

Good luck :)

Re: Scene Size vs Lighting

Posted: Fri Oct 11, 2019 10:25 pm
by SGR FA
Hi, Thanks for your answer !

I'll try to change units but because some of my materials use spectral medium data (unit based), it may brake something...

Code: Select all

  <medium>
    <name>...</name>
    <precedence>10</precedence>
    <basic>
      <ior>...</ior>
      <cauchy_b_coeff>0</cauchy_b_coeff>
      <max_extinction_coeff>1</max_extinction_coeff>
      <fast_sss>false</fast_sss>
      <absorption_coefficient>
        <constant>
          <regular_tabulated>
            <start_wavelength>...</start_wavelength>
            <end_wavelength>...</end_wavelength>
            <num_values>...</num_values>
               ...
        </regular_tabulated>
        </constant>
      </absorption_coefficient>
    </basic>
  </medium>
I can't see how I'll find settings in order to get comparable images : in my scene, camera is in a room and it looks outside with differents landscapes (but same envmap).