[Radiance-general] perfect specular reflection in rtrace

[Antoine Bugeat]

Hello all,

First, thank you very much for your quick answers.

If I understand correctly, among the possible options for solving my
problem, the simplest is to replace the perfect specular "plastic" by a
"mirror" material to have a "virtual source" calculation (I agree that 100%
of reflection is totally not real but it's just for this case to understand
the calculation).

void mirror M_Spec
0
0
3 1 1 1

But I still get 0...

As a reminder, I use these radiance parameters (the same as DAYSIM except
that I increase the -dr):
-I -aa 0.1 -ab 5 -ad 1000 -ar 300 -as 20 -dj 0 -dr 5 -ds 0.2 -dp 512 -lr 6
-lw 0.004 -st 0.1 -oov

In parallel, I found a paper written by Roland Schregle (Lucerne University
2015) with an extension of Radiance about photon mapping for caustics
reflection. It looks pretty complex and I think (and I hope) that I can
solve my problem without using this.

Best Regards,

Antoine



2017-10-12 22:45 GMT+02:00 Jan Wienold <jan.wienold at epfl.ch>:

> Hi Antoine,
> specular reflections are not traced at all to light sources in the ambient
> calculation (which you invoke by -I). Only to glow material. Thats why also
> the reflections of the sun on glass-material is not captured by rtrace -I.
> So either you use mirror material and a -dr >2 or you calculate a
> 180degree fisheye on you point and calculate the illuminace from the image.
> The view rays for the image are traced via specular surfaces towards light
> sources.
> Jan
>
>
> On 12 October 2017 19:22:28 CEST, Antoine Bugeat <bugeatantoine at gmail.com>
> wrote:
>>
>> Hello all,
>>
>> I'm a civil engineering student and I'm trying to compute the impact of
>> specular reflections in a street "canyon".
>> My problem is:
>> I use rtrace function with the basic parameters, the same as DAYSIM uses
>> (-I -aa 0.1 -ab 5 -ad 1000 -ar 300 -as 20 -dj 0 -dr 5 -ds 0.2 -dp 512
>> -lr 6 -lw 0.004 -st 0.1 -oov)
>> My sky and sun description come from gendaylit.
>> My wall is defined by a perfect specular plastic and the ground is
>> defined by a diffuse material.
>>
>> When I do the simulation, I get illogical results as if the specular
>> reflection of the walls had no impact.
>>
>> So, I tried to simulate a really simple scene with only one *specular
>> surface*:
>>
>> void plastic M_Spec
>> 0
>> 0
>> 5 0 0 0 1 0
>>
>> M_Spec polygon 1
>> 0
>> 0
>> 12 -5.0 0.0 -5.0
>> -5.0 0.0 5.0
>> 5.0 0.0 5.0
>> 5.0 0.0 -5.0
>>
>> My *source* is described as a sun perfectly perpendicular to the surface:
>>
>> void light solar
>> 0
>> 0
>> 3 1000 1000 1000
>>
>> solar source sun
>> 0
>> 0
>> 4 0.0 -1.0 0.0 0.5
>>
>> And the *sensor* is between the surface and the source and is regarding
>> right to the surface:
>>
>> 0.0 -5.0 0.0 0.0 1.0 0.0
>>
>> And in this case, I get 0 after my rtrace simulation.
>> I tried to vary some parameters of rtrace (direct and specular
>> parameters) but it change nothing I still get 0.
>>
>> Thank you for your help.
>>
>> Antoine Bugeat
>>
>>
>>
>>
>>
>>
> --
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>
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