As promised, I have put together two test scenes using eval_pigment() 
and trace(). The other files are used or can be used with the tests. 
Note: For the carpet scene, you need first to write data to file. This 
is explained within the scene file.

Enjoy!

-- 
Thomas

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Attachments:
Download 'eval_pigment.zip' (1006 KB)

Thanks for that!
Apparently I had an eval_pigment.zip in my download directory already from
3/4/2016 ...  :O
Way too many macros and tools and scene files, etc. to keep up with, which is a
good thing, I guess.

For general information purposes,
eval_pigment is a macro that is defined in functions.inc as shown below.

-----------------------------------------------
#macro eval_pigment(pigm, vec)
    #local fn = function { pigment { pigm } }
    #local result = (fn(vec.x, vec.y, vec.z));
    result
#end
-----------------------------------------------

I think that
jpeg "Oriental Carpets/Carpet_01.jpg"
ought to be
jpeg "Carpet_01.jpg"

I see:
#declare WriteStrands = off; //set to 'on' for the first pass.

Isn't there a way to just check if the file exists, and if not, create it?
I looked - but it's not clear that this is possible.
Seemed like a useful and desirable feature to be added, if that's the case.


Also, something just caught my eye in that older version:
It seems that the Lum macro tries to evaluate the r, g, and b values, take 1/3
of that sum, and if that's less than 0.5, put a RED cylinder instead of a blue.
 But at the left front of the render, there's a red cylinder sitting atop a high
part of the heightfield where everything else is blue.   Seems anomalous.

old zip attached here for those who want to play along.

Post a reply to this message

Attachments:
Download 'eval_pigment.zip' (104 KB)

Le 07/07/2016 16:02, Bald Eagle a écrit :
> Isn't there a way to just check if the file exists, and if not, create it?
> I looked - but it's not clear that this is possible.
> Seemed like a useful and desirable feature to be added, if that's the case.

isn't *file_exists(S)* part of the solution ?

http://wiki.povray.org/content/Reference:Numeric_Expressions

Post a reply to this message

Le_Forgeron <jgr### [at] freefr> wrote:
> isn't *file_exists(S)* part of the solution ?
>
> http://wiki.povray.org/content/Reference:Numeric_Expressions

Indeed, my friend, it is.

file_exists(S)
Attempts to open the file specified by the string S. The current directory and
all library directories specified by the Library_Path or +L options are also
searched. See Library Paths for details. Returns 1 if successful and 0 if
unsuccessful.

Although I suspected this existed, I did not think to look under "Numeric
Expressions" - I was looking under #read, #write, #append, etc.

I was hoping that there would be a similar example to

#fopen FILE_HANDLE_IDENTIFIER "mydata.txt" read
#while (defined(FILE_HANDLE_IDENTIFIER))
  #read (FILE_HANDLE_IDENTIFIER,Var1,Var2,Var3)
  ...
#end

for the file commands, but alas, no.


So here ya go:
############################################################################


#version 3.7;
global_settings {assumed_gamma 1.0}
#include "debug.inc"
  Set_Debug (true)
#declare FILENAME = "TestFile.txt";
//#declare FILE_HANDLE_IDENTIFIER = 1;

#declare ONE = 0; #declare TWO = 0; #declare THREE = 0; #declare FOUR = 0;
#declare FIVE = 0;

#declare Existence = file_exists (FILENAME);
// Attempts to open the file specified by the string S.
// The current directory and all library directories specified by the
Library_Path or +L options are also searched.
// See Library Paths for details. Returns 1 if successful and 0 if unsuccessful.

#debug "\n"
#debug
"#######################################################################################################\n"

#debug concat("Checking for existence of file ", FILENAME, " ... \n")
#declare Existence = file_exists (FILENAME);
#if (Existence = 1)
 #debug concat ("Directive 'file_exists (FILENAME)' = ", str (Existence, 1, 1),
"    File ", FILENAME, " exists. \n")
#else
 #debug concat ("Directive 'file_exists (FILENAME)' = ", str (Existence, 1, 1),
"    File ", FILENAME, " does not exist. \n")
#end
#debug "\n"

//---------------------------------------------------------------------------------------------------------------------
----------

#debug concat("Opening file ", FILENAME, " for writing ... \n")
#fopen  FILE_HANDLE_IDENTIFIER FILENAME write
#debug concat("Writing data to file ... \n")
#write (FILE_HANDLE_IDENTIFIER, 1, ", ", 2, ", ", 3, ", ", 4, ", ", 5,  ", \n")
#write (FILE_HANDLE_IDENTIFIER, 6, ", ", 7, ", ", 8, ", ", 9, ", ", 10, "\n")
#debug concat("Closing file ... \n")
#fclose FILE_HANDLE_IDENTIFIER
#debug "\n"

//---------------------------------------------------------------------------------------------------------------------
----------

#debug concat("Checking for existence of file ", FILENAME, " ... \n")
#declare Existence = file_exists (FILENAME);
#if (Existence = 1)
 #debug concat ("Directive 'file_exists (FILENAME)' = ", str (Existence, 1, 1),
"    File ", FILENAME, " exists. \n")
#else
 #debug concat ("Directive 'file_exists (FILENAME)' = ", str (Existence, 1, 1),
"    File ", FILENAME, " does not exist. \n")
#end
#debug "\n"

//---------------------------------------------------------------------------------------------------------------------
----------

#declare Existence = file_exists (FILENAME);
#if (Existence = 1)
 #debug concat("Opening file ", FILENAME, " for reading ... \n")
 #debug "\n"
 #fopen  FILE_HANDLE_IDENTIFIER FILENAME read
 // If you attempt to read past end-of-file, the file is automatically closed
and the FILE_HANDLE_IDENTIFIER is deleted from the symbol table.
 // This means that the boolean function defined(FILE_HANDLE_IDENTIFIER) can be
used to detect end-of-file.

 #while (defined (FILE_HANDLE_IDENTIFIER))
  #debug "File open, reading data from file... \n"
  #read (FILE_HANDLE_IDENTIFIER, ONE, TWO, THREE, FOUR, FIVE)
  // output 5-term color expression data
  #declare Vector = <ONE, TWO, THREE, FOUR, FIVE>;
  #debug concat( "Vector.x =        ", str(Vector.x, 3, 0), "\n")
  #debug concat( "Vector.u =        ", str(Vector.u, 3, 0), "\n\n")
  #debug concat( "Vector.y =        ", str(Vector.y, 3, 0), "\n")
  #debug concat( "Vector.v =        ", str(Vector.v, 3, 0), "\n\n")
  #debug concat( "Vector.z =        ", str(Vector.z, 3, 0), "\n\n")
  #debug concat( "Vector.t =        ", str(Vector.t, 3, 0), "\n")
  #debug concat( "Vector.filter =   ", str(Vector.filter, 3, 0), "\n\n")
  #debug concat( "Vector.transmit = ", str(Vector.transmit, 3, 0), "\n\n")
 #end

 #debug "End of file (EOF) reached. File automatically closed. \n"

 #fclose FILE_HANDLE_IDENTIFIER // just to make sure
#else
 #debug "File ", FILENAME, " does not exist. Cannot open for reading. \n"
#end // end if

#debug
"#######################################################################################################\n"
#debug "\n"

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Attachments:
Download 'filecommands.pov.txt' (4 KB)

On 7-7-2016 16:02, Bald Eagle wrote:
> Thanks for that!
> Apparently I had an eval_pigment.zip in my download directory already from
> 3/4/2016 ...  :O
> Way too many macros and tools and scene files, etc. to keep up with, which is a
> good thing, I guess.

I totally forgot about that one...

> [snip]
> I think that
> jpeg "Oriental Carpets/Carpet_01.jpg"
> ought to be
> jpeg "Carpet_01.jpg"

Absolutely. Escaped my scrutiny ;-)

>
> I see:
> #declare WriteStrands = off; //set to 'on' for the first pass.
>
> Isn't there a way to just check if the file exists, and if not, create it?
> I looked - but it's not clear that this is possible.
> Seemed like a useful and desirable feature to be added, if that's the case.
>

LeForgeron gave us the solution. I confess that I had not been aware of 
that possibility. One more reason to play :-)

>
> Also, something just caught my eye in that older version:
> It seems that the Lum macro tries to evaluate the r, g, and b values, take 1/3
> of that sum, and if that's less than 0.5, put a RED cylinder instead of a blue.
>  But at the left front of the render, there's a red cylinder sitting atop a high
> part of the heightfield where everything else is blue.   Seems anomalous.
>

No idea.


-- 
Thomas

Post a reply to this message

On 7-7-2016 16:02, Bald Eagle wrote:
> I see:
> #declare WriteStrands = off; //set to 'on' for the first pass.
>
> Isn't there a way to just check if the file exists, and if not, create it?
> I looked - but it's not clear that this is possible.
> Seemed like a useful and desirable feature to be added, if that's the case.
>

In fact, there is a simple reason why I did not use the file_exists(S) 
function, now that I think about it. It is that you may want to test 
different settings before choosing the final ones (at least that is how 
I work) and so - except for the very first time - there is always a file 
present.

-- 
Thomas

Post a reply to this message

Am 09.07.2016 um 08:52 schrieb Thomas de Groot:
> On 7-7-2016 16:02, Bald Eagle wrote:
>> I see:
>> #declare WriteStrands = off; //set to 'on' for the first pass.
>>
>> Isn't there a way to just check if the file exists, and if not, create
>> it?
>> I looked - but it's not clear that this is possible.
>> Seemed like a useful and desirable feature to be added, if that's the
>> case.
>>
> 
> In fact, there is a simple reason why I did not use the file_exists(S)
> function, now that I think about it. It is that you may want to test
> different settings before choosing the final ones (at least that is how
> I work) and so - except for the very first time - there is always a file
> present.

You could use something like:

    #declare WriteStrands = off; // set to 'on' to force re-writing
    ...
    #if (!file_exists(...)) #declare WriteStrands = on; #end

Post a reply to this message

On 9-7-2016 12:38, clipka wrote:
> Am 09.07.2016 um 08:52 schrieb Thomas de Groot:
>> On 7-7-2016 16:02, Bald Eagle wrote:
>>> I see:
>>> #declare WriteStrands = off; //set to 'on' for the first pass.
>>>
>>> Isn't there a way to just check if the file exists, and if not, create
>>> it?
>>> I looked - but it's not clear that this is possible.
>>> Seemed like a useful and desirable feature to be added, if that's the
>>> case.
>>>
>>
>> In fact, there is a simple reason why I did not use the file_exists(S)
>> function, now that I think about it. It is that you may want to test
>> different settings before choosing the final ones (at least that is how
>> I work) and so - except for the very first time - there is always a file
>> present.
>
> You could use something like:
>
>     #declare WriteStrands = off; // set to 'on' to force re-writing
>     ...
>     #if (!file_exists(...)) #declare WriteStrands = on; #end
>

But, that would always set it to on, even when you want it to be off, or 
do I misunderstand this?

-- 
Thomas

Post a reply to this message

Am 09.07.2016 um 13:17 schrieb Thomas de Groot:
> On 9-7-2016 12:38, clipka wrote:
>> Am 09.07.2016 um 08:52 schrieb Thomas de Groot:
>>> On 7-7-2016 16:02, Bald Eagle wrote:
>>>> I see:
>>>> #declare WriteStrands = off; //set to 'on' for the first pass.
>>>>
>>>> Isn't there a way to just check if the file exists, and if not, create
>>>> it?
>>>> I looked - but it's not clear that this is possible.
>>>> Seemed like a useful and desirable feature to be added, if that's the
>>>> case.
>>>>
>>>
>>> In fact, there is a simple reason why I did not use the file_exists(S)
>>> function, now that I think about it. It is that you may want to test
>>> different settings before choosing the final ones (at least that is how
>>> I work) and so - except for the very first time - there is always a file
>>> present.
>>
>> You could use something like:
>>
>>     #declare WriteStrands = off; // set to 'on' to force re-writing
>>     ...
>>     #if (!file_exists(...)) #declare WriteStrands = on; #end
>>
> 
> But, that would always set it to on, even when you want it to be off, or
> do I misunderstand this?

It would always set it to on _if_ the file does not already exist, so
you don't need to manually set it to on for the first run.

Of course if there are any use cases where you might want to have _no_
file at all, then this is of no use.

Post a reply to this message

On 9-7-2016 13:42, clipka wrote:
> Am 09.07.2016 um 13:17 schrieb Thomas de Groot:
>> On 9-7-2016 12:38, clipka wrote:
>>> Am 09.07.2016 um 08:52 schrieb Thomas de Groot:
>>>> On 7-7-2016 16:02, Bald Eagle wrote:
>>>>> I see:
>>>>> #declare WriteStrands = off; //set to 'on' for the first pass.
>>>>>
>>>>> Isn't there a way to just check if the file exists, and if not, create
>>>>> it?
>>>>> I looked - but it's not clear that this is possible.
>>>>> Seemed like a useful and desirable feature to be added, if that's the
>>>>> case.
>>>>>
>>>>
>>>> In fact, there is a simple reason why I did not use the file_exists(S)
>>>> function, now that I think about it. It is that you may want to test
>>>> different settings before choosing the final ones (at least that is how
>>>> I work) and so - except for the very first time - there is always a file
>>>> present.
>>>
>>> You could use something like:
>>>
>>>     #declare WriteStrands = off; // set to 'on' to force re-writing
>>>     ...
>>>     #if (!file_exists(...)) #declare WriteStrands = on; #end
>>>
>>
>> But, that would always set it to on, even when you want it to be off, or
>> do I misunderstand this?
>
> It would always set it to on _if_ the file does not already exist, so
> you don't need to manually set it to on for the first run.
>
> Of course if there are any use cases where you might want to have _no_
> file at all, then this is of no use.
>

I think you misunderstand my use of the on/off switch. The writing away 
of data is only meant as time saving later on when reading the data 
(always faster than having to do the complete calculations for each 
run). So, the switching off of the writing section (once you are 
satisfied with the written data) is essential. A file_exist switch can 
only make sense to check the existence of a file in the "Read" section 
of the macro.

-- 
Thomas

Post a reply to this message

Am 10.07.2016 um 09:00 schrieb Thomas de Groot:
> On 9-7-2016 13:42, clipka wrote:
>> Am 09.07.2016 um 13:17 schrieb Thomas de Groot:
>>> On 9-7-2016 12:38, clipka wrote:
>>>> Am 09.07.2016 um 08:52 schrieb Thomas de Groot:
>>>>> On 7-7-2016 16:02, Bald Eagle wrote:
>>>>>> I see:
>>>>>> #declare WriteStrands = off; //set to 'on' for the first pass.
>>>>>>
>>>>>> Isn't there a way to just check if the file exists, and if not,
>>>>>> create
>>>>>> it?
>>>>>> I looked - but it's not clear that this is possible.
>>>>>> Seemed like a useful and desirable feature to be added, if that's the
>>>>>> case.
>>>>>>
>>>>>
>>>>> In fact, there is a simple reason why I did not use the file_exists(S)
>>>>> function, now that I think about it. It is that you may want to test
>>>>> different settings before choosing the final ones (at least that is
>>>>> how
>>>>> I work) and so - except for the very first time - there is always a
>>>>> file
>>>>> present.
>>>>
>>>> You could use something like:
>>>>
>>>>     #declare WriteStrands = off; // set to 'on' to force re-writing
>>>>     ...
>>>>     #if (!file_exists(...)) #declare WriteStrands = on; #end
>>>>
>>>
>>> But, that would always set it to on, even when you want it to be off, or
>>> do I misunderstand this?
>>
>> It would always set it to on _if_ the file does not already exist, so
>> you don't need to manually set it to on for the first run.
>>
>> Of course if there are any use cases where you might want to have _no_
>> file at all, then this is of no use.
> 
> I think you misunderstand my use of the on/off switch.

Not at all. But you apparently misunderstand my use of `file_exists()` ;)

> The writing away
> of data is only meant as time saving later on when reading the data
> (always faster than having to do the complete calculations for each
> run). So, the switching off of the writing section (once you are
> satisfied with the written data) is essential. A file_exist switch can
> only make sense to check the existence of a file in the "Read" section
> of the macro.

No, the `file_exists()` test makes perfect sense before the file
generation. It's pretty simple:

- You use `#declare WriteStrands = on;` while experimenting, forcing a
(re-)write on every run.

- You use `#declare WriteStrands = off;` once you're ok, suppressing a
re-write.

- In case the file does not yet exist, the `#if (!file_exists(...))
#declare WriteStrands = on; #end` overrides your choice and forces a
write, thus making sure that the finished scene can be rendered as-is,
with no tampering necessary even if the data file happens to be missing
for some reason.

Post a reply to this message

On 10-7-2016 15:28, clipka wrote:
> Am 10.07.2016 um 09:00 schrieb Thomas de Groot:
>> On 9-7-2016 13:42, clipka wrote:
>>> Am 09.07.2016 um 13:17 schrieb Thomas de Groot:
>>>> On 9-7-2016 12:38, clipka wrote:
>>>>> Am 09.07.2016 um 08:52 schrieb Thomas de Groot:
>>>>>> On 7-7-2016 16:02, Bald Eagle wrote:
>>>>>>> I see:
>>>>>>> #declare WriteStrands = off; //set to 'on' for the first pass.
>>>>>>>
>>>>>>> Isn't there a way to just check if the file exists, and if not,
>>>>>>> create
>>>>>>> it?
>>>>>>> I looked - but it's not clear that this is possible.
>>>>>>> Seemed like a useful and desirable feature to be added, if that's the
>>>>>>> case.
>>>>>>>
>>>>>>
>>>>>> In fact, there is a simple reason why I did not use the file_exists(S)
>>>>>> function, now that I think about it. It is that you may want to test
>>>>>> different settings before choosing the final ones (at least that is
>>>>>> how
>>>>>> I work) and so - except for the very first time - there is always a
>>>>>> file
>>>>>> present.
>>>>>
>>>>> You could use something like:
>>>>>
>>>>>     #declare WriteStrands = off; // set to 'on' to force re-writing
>>>>>     ...
>>>>>     #if (!file_exists(...)) #declare WriteStrands = on; #end
>>>>>
>>>>
>>>> But, that would always set it to on, even when you want it to be off, or
>>>> do I misunderstand this?
>>>
>>> It would always set it to on _if_ the file does not already exist, so
>>> you don't need to manually set it to on for the first run.
>>>
>>> Of course if there are any use cases where you might want to have _no_
>>> file at all, then this is of no use.
>>
>> I think you misunderstand my use of the on/off switch.
>
> Not at all. But you apparently misunderstand my use of `file_exists()` ;)

That was a hypothesis I had not considered of course. ;-)

>
>> The writing away
>> of data is only meant as time saving later on when reading the data
>> (always faster than having to do the complete calculations for each
>> run). So, the switching off of the writing section (once you are
>> satisfied with the written data) is essential. A file_exist switch can
>> only make sense to check the existence of a file in the "Read" section
>> of the macro.
>
> No, the `file_exists()` test makes perfect sense before the file
> generation. It's pretty simple:
>
> - You use `#declare WriteStrands = on;` while experimenting, forcing a
> (re-)write on every run.
>
> - You use `#declare WriteStrands = off;` once you're ok, suppressing a
> re-write.
>
> - In case the file does not yet exist, the `#if (!file_exists(...))
> #declare WriteStrands = on; #end` overrides your choice and forces a
> write, thus making sure that the finished scene can be rendered as-is,
> with no tampering necessary even if the data file happens to be missing
> for some reason.
>

I see. Not sure if I want to do it that way though. I keep this in mind 
for when I 'really' need it :-)

-- 
Thomas

Post a reply to this message

"Bald Eagle" <cre### [at] netscapenet> wrote:

>
> For general information purposes,
> eval_pigment is a macro that is defined in functions.inc as shown below.
>
> -----------------------------------------------
> #macro eval_pigment(pigm, vec)
>     #local fn = function { pigment { pigm } }
>     #local result = (fn(vec.x, vec.y, vec.z));
>     result
> #end
> -----------------------------------------------

It's always been interesting to me that the macro was designed to work only with
the r-g-b color components, and not with the f and t components as well. I
assume there's a reason for that (a technical one?); but evaluating a color like
rgb <.3,.5,.7,.4,.2> will return just the 'opague' colors, not the "colors +
f-and-t mix."

Or maybe my own logic about 'color mixing' is in error, when it comes to
*translucent* color shades (?). I admit that the effects of f and t on a color
are not the same as, say, adding *white* to get a pastel tint. But eval_pigment,
as-is, gives a kind of false result when working with translucency-- or so it
seems.

Post a reply to this message

Am 12.07.2016 um 07:20 schrieb Kenneth:

>> For general information purposes,
>> eval_pigment is a macro that is defined in functions.inc as shown below.
>>
>> -----------------------------------------------
>> #macro eval_pigment(pigm, vec)
>>     #local fn = function { pigment { pigm } }
>>     #local result = (fn(vec.x, vec.y, vec.z));
>>     result
>> #end
>> -----------------------------------------------
> 
> It's always been interesting to me that the macro was designed to work only with
> the r-g-b color components, and not with the f and t components as well. I
> assume there's a reason for that (a technical one?); but evaluating a color like
> rgb <.3,.5,.7,.4,.2> will return just the 'opague' colors, not the "colors +
> f-and-t mix."

And what exactly would make you think so?

If you try it out, you'll find that eval_pigment() works perfectly fine
with full-fledged rgbft colours.

Maybe you somehow got the impression that the `.x`, `.y` and `.z`
referred to the pigment colour's components? They don't. They instead
refer to the input point, passing the individual coordinates as separate
parameters to the pigment function.

Post a reply to this message

On 12-7-2016 8:00, clipka wrote:
> If you try it out, you'll find that eval_pigment() works perfectly fine
> with full-fledged rgbft colours.
>
> Maybe you somehow got the impression that the `.x`, `.y` and `.z`
> referred to the pigment colour's components? They don't. They instead
> refer to the input point, passing the individual coordinates as separate
> parameters to the pigment function.
>

That is interesting! I did not know that but it makes sense indeed. Good 
to know.

-- 
Thomas

Post a reply to this message