POV-Ray : Newsgroups : povray.binaries.images : some issues Server Time
3 Jul 2024 01:00:40 EDT (-0400)
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From: CAS
Subject: some issues
Date: 28 Oct 2014 00:00:02
Message: <web.544f1448bd8ef5736a92a3a00@news.povray.org>
This is my experiment, I want to output three pictures:
The first is the intersection point.My aim is to get coordinates of intersection
point.The second is the normal vector.My aim is to get normal vector of
intersection point.The third is the scene image.My purpose is to check whether
my input is correspondence with my output.But I found the intersection and
normal  is wrong.I can not get the coordinates and normal of each intersection
point from my "intersection.bmp" and "normal.bmp".Maybe something was wrong in
my codes.I have uploaded my codes,expecting someone to give me a help.Thanks.


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Attachments:
Download 'megapov1.zip' (980 KB)

From: Le Forgeron
Subject: Re: some issues
Date: 28 Oct 2014 03:53:10
Message: <544f4b66$1@news.povray.org>
Le 28/10/2014 04:58, CAS a écrit :
> This is my experiment, I want to output three pictures:
> The first is the intersection point.My aim is to get coordinates of intersection
> point.The second is the normal vector.My aim is to get normal vector of
> intersection point.The third is the scene image.My purpose is to check whether
> my input is correspondence with my output.But I found the intersection and
> normal  is wrong.I can not get the coordinates and normal of each intersection
> point from my "intersection.bmp" and "normal.bmp".Maybe something was wrong in
> my codes.I have uploaded my codes,expecting someone to give me a help.Thanks.
> 

Your image are bmp, the range of channel in bmp (32 bits true color) is
too small for the information you want.

Give a try to HDR output (+FH).

http://megapov.inetart.net/manual-1.2.1/megapov0121.html#hdr

Next step: having a look in source code of megapov to understand the
data provided by f_output_*

A shame there is no sample scene for pprocess with intersection or normal.



-- 
Just because nobody complains does not mean all parachutes are perfect.


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From: Alain
Subject: Re: some issues
Date: 28 Oct 2014 17:39:05
Message: <54500cf9@news.povray.org>
Le 14-10-28 03:53, Le_Forgeron a écrit :
> Le 28/10/2014 04:58, CAS a écrit :
>> This is my experiment, I want to output three pictures:
>> The first is the intersection point.My aim is to get coordinates of intersection
>> point.The second is the normal vector.My aim is to get normal vector of
>> intersection point.The third is the scene image.My purpose is to check whether
>> my input is correspondence with my output.But I found the intersection and
>> normal  is wrong.I can not get the coordinates and normal of each intersection
>> point from my "intersection.bmp" and "normal.bmp".Maybe something was wrong in
>> my codes.I have uploaded my codes,expecting someone to give me a help.Thanks.
>>
>
> Your image are bmp, the range of channel in bmp (32 bits true color) is
> too small for the information you want.
>
> Give a try to HDR output (+FH).
>
> http://megapov.inetart.net/manual-1.2.1/megapov0121.html#hdr
>
> Next step: having a look in source code of megapov to understand the
> data provided by f_output_*
>
> A shame there is no sample scene for pprocess with intersection or normal.
>
>
>

An alternative would be to use +fn16 to generate a PNG image at 16 bit 
per channel.


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From: Le Forgeron
Subject: Re: some issues
Date: 29 Oct 2014 16:12:54
Message: <54514a46$1@news.povray.org>
On 28/10/2014 22:40, Alain wrote:
> Le 14-10-28 03:53, Le_Forgeron a écrit :
>> Le 28/10/2014 04:58, CAS a écrit :
>>> This is my experiment, I want to output three pictures:
>>> The first is the intersection point.My aim is to get coordinates of
>>> intersection
>>> point.The second is the normal vector.My aim is to get normal vector of
>>> intersection point.The third is the scene image.My purpose is to
>>> check whether
>>> my input is correspondence with my output.But I found the
>>> intersection and
>>> normal  is wrong.I can not get the coordinates and normal of each
>>> intersection
>>> point from my "intersection.bmp" and "normal.bmp".Maybe something was
>>> wrong in
>>> my codes.I have uploaded my codes,expecting someone to give me a
>>> help.Thanks.
>>>
>>
>> Your image are bmp, the range of channel in bmp (32 bits true color) is
>> too small for the information you want.
>>
>> Give a try to HDR output (+FH).
>>
>> http://megapov.inetart.net/manual-1.2.1/megapov0121.html#hdr
>>
>> Next step: having a look in source code of megapov to understand the
>> data provided by f_output_*
>>
>> A shame there is no sample scene for pprocess with intersection or
>> normal.
>>
>>
>>
> 
> An alternative would be to use +fn16 to generate a PNG image at 16 bit
> per channel.

Right, it is easier with png.

I now had a playsession with megapov and I have the following feelings:

* normal is probably normalized (good), but you'd better expect a -1 to
1 range, so to get some correct colours, you need to scale and shift it
a bit (as only value in the 0 to 1 range are good for generating
different colours):

  post_process{
    function { 0.5+0.5*f_output_inormal_x(x,y) }
    function { 0.5+0.5*f_output_inormal_y(x,y) }
    function { 0.5+0.5*f_output_inormal_z(x,y) }
    function { f_output_alpha(x,y) }
    save_file concat("nn_",output_filename(0))

* intersection point is even stronger, the value is raw, so you need an
even better adaptation to make a descent colours out of them. (which
mean you have to know what voxel the camera is looking at for a better
formula)

* +UA and png is indeed recommend (+FN16 !) to be able to distinguish
the part with no intersection

  post_process{
    function { 0.5+.05*f_output_ipoint_x(x,y) }
    function { 0.5+.05*f_output_ipoint_y(x,y) }
    function { 0.5+.05*f_output_ipoint_z(x,y) }
    function { f_output_alpha(x,y) }
    save_file concat("ii_",output_filename(0))
  }

* Extracting the data is only a matter of inverting the previous
transformation: convert the pixel's color as float between 0 and 1, (max
colour's channel is 1, min is 0), and just revert the transformation
(such as 0.5+0.05*value --> value = (channel-0.5)*20 ).

* Reading pprocess.inc is mandatory, as many macro are needed to define
the right functions.

* png_write_finish_row is no more, so compiling was interesting... just
comment that functions from png_pov.cpp (it is used with partial
image... just avoid them now)


-- 
IQ of crossposters with FU: 100 / (number of groups)
IQ of crossposters without FU: 100 / (1 + number of groups)
IQ of multiposters: 100 / ( (number of groups) * (number of groups))


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