POV-Ray : Newsgroups : povray.advanced-users : Radiosity rendering depends on camera direction? : Re: Radiosity rendering depends on camera direction? Server Time: 26 Jun 2019 19:58:04 GMT
  Re: Radiosity rendering depends on camera direction?  
From: Alain
Date: 8 Apr 2019 17:06:06
Le 19-04-07 à 09:28, Tamas Gunda a écrit :
> Alain <kua### [at] videotronca> wrote:
>> Strange, radiosity have no effect of the geometry and should be
>> independent of the camera's location and orientation.
>>
>> What can happen is a difference on what areas radiosity is sampling. If
>> that's the case, increasing the count value should help, also, using the
>> two values variant often help :
>> count 175 25000
>>
>> You may also want to reduce the value for pretrace_end. Default is 0.04.
>> Try 0.01, 0.005 or 0.0025.
>>
>> Looking at the dark end and you really need more samples. Quadrupling
>> your count value may not be quite enough. You may also need to increase
>> the recursion_limit value to 4 or maybe 5. Also, reducing minimum_reuse
>> could also help. Default is 0.015. Try 0.01 down to 0.004.
>>
>> Adding some roundness to the edges can do a lot in reducing the
>> artefacts in the darker areas. A clipped cylinder will do the trick.
>>
>> If you can post the source of your scene, it'll be easier to diagnose
>> the issue and help you.
>>
>>
>>
>> Alain
> 
> Thanks for the reply. Well, I tried sytematically many variations. It helped to
> decrease the artefacts, however, the main problem could not be solved. It is
> mostly influenced when playing with the radiosity brightness and finish/diffuse
> values of the walls, but the effect of a given setting is different on the
> different faces. Inspect www.gunda.hu/cube/povray again: In the third picture
> some of the differences between the cube sides disappeared (the upper and the
> right), while others became stronger. In other words, it seems to me that nearly
> every setting influences more or less the brightness of the generated pictures,
> and this influence depends somehow on the direction of the camera.
> 
> 
> The radiosity settings used:
> 
> #if (radio)
>   global_settings {
>      ambient_light 0
>      radiosity {
>        pretrace_start  64/image_width
>        pretrace_end    4/image_width  //8
>        count 250 25000  //150
>        nearest_count 10
Using a larger value, op to 20, can help in smoothing some rough edges.
>        error_bound 0.33 //0.5
>        recursion_limit 4 //3
Try 5 to bring some more light down the hallway.
>        low_error_factor 0.5  //0.5
Reducing this may eliminate some artefacts.
>        gray_threshold 0.5  //0.5
Should be kept at the default of 0
>        minimum_reuse 0.004 //0.025
>        maximum_reuse 0.2 //0.2
>        brightness 1.3 //1.5
Should be left at default of 1
>        adc_bailout 0.01 //0.01
Try something smaller, like 1/256. It can help when you have very bright 
and dark areas.
>        media m_media
>        //max_sample 1
>        //normal on
>      }
>    }
> 
> #else
>   global_settings {ambient_light .1}
> 
> #end
> 
> 
> Tamas
> 
> 

Just an idea :
Try rendering it all in one go, then, project onto a box or sphere :

First, render using this camera :

camera{
  spherical
  angle 360
  up y
  right x*2
}
Render with a 2:1 aspect ratio with radiosity.
The image will look a little strange with both ends of the hallway 
visible at the same time.
You may want to do a test without radiosity first to get a feel of how 
it work.

Next, project the resulting image onto a box :
box{-1, 1
  pigment{image_map{ png"ImageName.png" map_type 1 scale <-1,1,1>}}
  finish{emission 1 diffuse 0 ambient 0}
}

Or a sphere :
sphere{0 1
  pigment{image_map{ png"ImageName.png" map_type 1 scale <-1,1,1>}}
  finish{emission 1 diffuse 0 ambient 0}
}

Render with a normal camera at <0,0,0> with no light.
If the image is to bright or dim, adjust emission to compensate.

As the whole scene was rendered as a single image, there can be no 
seams, allowing you to use more relaxed radiosity settings.
The final renders will be fast as the geometry is simple, there are no 
light, and only an image_map to evaluate.


Alain


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