"muyu" <lsy### [at] gmailcom> wrote:
> from [povray.general]
> Am 20.03.2017 um 11:38 schrieb muyu:
>
> > Thanks. 1) Regarding my simulations, around 50% of the light is reflected in
> > near-infrared. So physically the expected error should be much less than 1%.
> > This should be neglible?
>
> > 2) However, I found almost 10%  under-estimates compared with the reference
> > using Monte Carlo method. What's the possible reasons for this? Should I
> > increase the brightness or the light intensity?
>
> No ideas at the moment. Maybe if you posted the resulting images, the
> distribution of light within the canopy might give a hint.
>
> You mentioned reflection above; did you also account for the transmitted
> light?
>
> Here it is the setting of the radiosity:
> #version 3.7;
> global_settings {
>    assumed_gamma 1.0
>    ambient_light 0.0
>    adc_bailout 0.0
>    max_trace_level 20
>
>    radiosity {
>       count 1500
>       error_bound 0.01
>       recursion_limit 20
>       nearest_count 10
>    }
> }
>
> // light--------------------------------------------------------------
> light_source{<0,36.397,100> color rgb<0,1,0> parallel}
>
> // ground ------------------------------------------------------------
> plane { <0,0,1>, 0
>         texture{ pigment{color rgb<0, 1, 0>}
>                  finish {ambient 0 diffuse 0.1590 0.0000}
>                } // end of texture
>       } // end of plane
>
> // leaves----------------------------------------------
> #declare leaf_text = texture {
> pigment {color rgb<0.0,1.0,0.0>}
> finish {ambient 0 diffuse 0.4957 0.4409}}
> disc {<9.5780,-10.5050,0.6040>, <0.7070,0.1830,0.6840>, 0.0500
> texture {leaf_text}}
> .....
>
> diffuse 0.4957 is front diffuse, 0.4409 is the transmitted light? Should I set
> rgbt or rgbf?
>
> Is this the right way to consider the multi-scattering using Radiosity? I have
> the impression that some processes are missing?
>
> Thax in advance.

Antialias = on
Antialias_Threshold = 0.1
Antialias_Depth = 2

Input_File_Name = "canopy_2_camera.pov"

width = 1000
height = 1000

Cyclic_Animation = on
Pause_when_Done = off

The reflectance of each pixel was calculated relative to the reference panel
with the same light source and camera setup
// the reference panel--------------------------------------------------------
plane { <0,0,1>, 0
        texture{ pigment{color rgb<0, 1, 0>}
                 finish {ambient 0 diffuse 1.0 0.0 conserve_energy}
               } // end of texture
      } // end of plane

Reflectance = (Simulation/Reference)^2.2

Is this calibration right? Thanks again.

Post a reply to this message

Attachments:
Download 'ref_plane.png' (6 KB)

Preview of image 'ref_plane.png'