On 04/17/2014 08:32 AM, CAS wrote:
> "CAS" <sup### [at] cstnetcn> wrote:
>> Alain <kua### [at] videotronca> wrote:

>>>> scott <sco### [at] scottcom> wrote:
>>>>>> Hello,everyone.I am a student.I am doing my graduation project recently.It is
>>>>>> simulating radiance with ray-tracing.I have done a test with pov.But I am
>>>>>> confronting a error with my result.Could anyboby help me check out my issue.Beg
>>>>>> a hot.I am a student.I am confronting the pressure of graduation.I feel so
>>>>>> worry.I have uploaded the whole process of my test,beg a hot help me!
>>>>>> "pov-xyz"is the location of each sphere.
>>>>>> "pov-ref"is the reflectivity of each sphere.
>>>>>> "pov.exr"is the output image by pov.
>>>>>> I have converted "pov.exr" to "pov.tiff".
>>>>>> "result"is my analyse.My issue was wrote in it.
>>>>>> Expecting somebody help me.Great gratitudes!
>>>>>
>>>>> Using a specular highlight on tiny spheres is going to give very
>>>>> unpredictable results, the output pixel value will highly depend on
>>>>> exactly where the ray hits the sphere compared to the highlight
>>>>> position. I zoomed in on your scene and rendered it, see attached, I
>>>>> also changed the background colour to red to highlight the spheres
>>>>> better. Do you see the problem?
>>>>>
>>>>> I would use boxes rather than spheres and use diffuse rather than
>>>>> specular reflection:
>>>>>
>>>>>     pigment{color rgb 1}
>>>>>     finish {
>>>>>      ambient 0
>>>>>      diffuse ref
>>>>>     }
>>>>> }
>>>>>
>>>>> That should give much more uniform results and not depend on where each
>>>>> ray hits the shapes. I don't know if that will solve your problem or not.
>>>>
>>>> I have modified the statements and done a test with your advice.I find the
>>>> result changed,but not what I wanted.Besides,I only have 40000 points ,if I used
>>>> box as my model, which needs two points to describle,but my input scene is as
>>>> "pov.tif".One point stands for one object,corresponding,with a reflectity.If I
>>>> used box,may need two point to descible a object,I doublt the scene is not my
>>>> wanted.
>>>>
>>>>
>>>>
>>>>
>>>
>>> You can use boxes instead of spheres without doubling the size of your
>>> file. Curently, you use this code to place your spheres:
>>> sphere {
>>>    <x1-center_x,y1-center_y,z1-center_z>,1.55
>>>    finish { ambient 0
>>>             emission 0
>>>             specular ref
>>>             }
>>>          }
>>>
>>> To use box, just use this code:
>>> box{-1.55, 1.55 // reduce slightly is you want to keep some gap.
>>> // The following line is the key...
>>>   translate <x1-center_x,y1-center_y,z1-center_z>
>>>    finish { ambient 0
>>>             emission 0
>>>             specular ref
>>>             }
>>>          }
>>>
>>>
>>> This will give you boxes with a width identical to the diameter of your
>>> spheres.
>>>
>>> Even beter, make an union containing all your objects:
>>>
>>> union{
>>> #fopen   Input_geom_file geom_file_name read
>>> #fopen   Input_spec_file spec_file_name read
>>> #while(defined(Input_geom_file))
>>>
>>>       #read(Input_geom_file, X1, Y1, Z1)
>>>       #read(Input_spec_file, Ref)
>>>
>>> box{-1.55, 1.55 // reduce slightly is you want to keep some gap.
>>> // The following line is the key...
>>>   translate <X1-Center_X,Y1-Center_Y,Z1-Center_Z>
>>>          }// Remove the texture from the objects
>>> #end
>>> // and apply it to all objects at once
>>>    finish { ambient 0
>>>             emission 0
>>>             specular Ref
>>>             }
>>> }// End of the union
>>>
>>> As the variable "n" is never used, I removed it.
>>>
>>> Finaly, a general recomendation: In all of your user defined variable,
>>> use at least ONE upper case letter. This ensure that you don't have any
>>> conflict with predefined variables and primitive. It also make it clear
>>> that those are YOUR variables. It can realy help when debugging your code.
>>>
>>>
>>>
>>>
>>> Alain
>>
>> Hello,I want to ask a question:
>> "try
>>   {
>>    Imf::RgbaChannels channels;
>>    if (options.grayscale)
>>     if (use_alpha)
>>      channels = WRITE_YA; // only write luminance & alpha
>>     else
>>      channels = WRITE_Y; // only write luminance
>>    else
>>     if (use_alpha)
>>      channels = WRITE_RGBA; // write RGB & alpha
>>     else
>>      channels = WRITE_RGB; // write RGB"
>>
>> this is a part of resource code in openexr.cpp,I want to write luminance
>> only,how can I set some parameters in pov?
>
> -UA :Sets alpha output off
> +Feg:output type 'e' grayscale output
> I set "-UA +Feg" in command line,but messages says :grayscale not currently
> supported whith output file format "e";But only openexr file supports luminance
> output.How can I solve this problem?
>
Currently PNG, and PPM are the only file formats that support grayscale 
output

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