I've been using functions in POV-Ray for years now (successfully)--pigment
functions, functions for isosurfaces, etc. Yet I've never been able to make
sense of the examples given in the docs at 3.2.1.6.5  "Declaring User-Defined
Color Functions". It's not the set-up of the functions themselves that are
mysterious, but the examples of their use.

Here are the two code lines given there:

#declare Vec = foo(1,2,3)

and

#declare Val = foo(2,3,4).gray

What do the values (1,2,3) and (2,3,4) represent? There's no explanation given,
and I can't figure it out intuitively. (Is it simply a shorthand way of saying
(1*x,2*y,3*z)?) I've read and re-read the sections preceding this one, yet still
don't have a clue.

Post a reply to this message

On 27-2-2013 10:34, Kenneth wrote:
> 3.2.1.6.5  "Declaring User-Defined Color Functions".

A bit difficult to find ;-)

in the 3.7 RC7 offline Docs: 3.3.1.8.5
in the online wiki Docs: 2.3.1.8.5

That said, I have been a bit confused too. I suppose the numbers stand 
for the x,y,z parameters of the function.

Thomas

Post a reply to this message

On 02/27/2013 07:39 AM, Thomas de Groot wrote:
> On 27-2-2013 10:34, Kenneth wrote:
>> 3.2.1.6.5  "Declaring User-Defined Color Functions".
>
> A bit difficult to find ;-)
>
> in the 3.7 RC7 offline Docs: 3.3.1.8.5
> in the online wiki Docs: 2.3.1.8.5

That's where I find them as well, so I don't know where Ken got his 
annotation ... perhaps 3.6 but hey that's ancient history right? It's 
usually more meaningful to say ... e.g: in the Reference 3.1.8.5

As far as the content at Reference 3.1.8.5 ... user defined functions is 
an advanced technique. If you've gotten that far there does seem to be a 
build in assumption ... not that big of a leap IMHO.

Post a reply to this message

James Holsenback <nom### [at] nonecom> wrote:
> On 02/27/2013 07:39 AM, Thomas de Groot wrote:
> > On 27-2-2013 10:34, Kenneth wrote:
> >> 3.2.1.6.5  "Declaring User-Defined Color Functions".
> >
> > A bit difficult to find ;-)
> >
> > in the 3.7 RC7 offline Docs: 3.3.1.8.5
> > in the online wiki Docs: 2.3.1.8.5
>
> That's where I find them as well, so I don't know where Ken got his
> annotation ... perhaps 3.6 but hey that's ancient history right? It's
> usually more meaningful to say ... e.g: in the Reference 3.1.8.5
>
> As far as the content at Reference 3.1.8.5 ... user defined functions is
> an advanced technique. If you've gotten that far there does seem to be a
> build in assumption ... not that big of a leap IMHO.

In the 3.7 RC6 help file that opens up for me it is section 3.2.1.6.5
I suppose I should be installing RC7.


For what it does:

#declare Vec = foo(1,2,3) returns the rgb value at the (x,y,z) coordinate
(1,2,3)


#declare Val = foo(2,3,4).gray does the same thing, but then converts it to a
single gray value based on rgb->grey conversion formula.


-tgq

Post a reply to this message

On 27-2-2013 15:43, James Holsenback wrote:
> That's where I find them as well, so I don't know where Ken got his
> annotation ... perhaps 3.6 but hey that's ancient history right? It's
> usually more meaningful to say ... e.g: in the Reference 3.1.8.5
>
> As far as the content at Reference 3.1.8.5 ... user defined functions is
> an advanced technique. If you've gotten that far there does seem to be a
> build in assumption ... not that big of a leap IMHO.
>

As for me, I have not gotten that far myself.  ;-)

Thomas

Post a reply to this message

Kenneth <kdw### [at] gmailcom> wrote:
> Here are the two code lines given there:

> #declare Vec = foo(1,2,3)

> and

> #declare Val = foo(2,3,4).gray

> What do the values (1,2,3) and (2,3,4) represent?

They mean whatever the function wants them to mean. The function
constructs the vector from those values.

-- 
                                                          - Warp

Post a reply to this message

On 02/27/2013 10:04 AM, Trevor G Quayle wrote:
> James Holsenback <nom### [at] nonecom> wrote:
>> On 02/27/2013 07:39 AM, Thomas de Groot wrote:
>>> On 27-2-2013 10:34, Kenneth wrote:
>>>> 3.2.1.6.5  "Declaring User-Defined Color Functions".
>>>
>>> A bit difficult to find ;-)
>>>
>>> in the 3.7 RC7 offline Docs: 3.3.1.8.5
>>> in the online wiki Docs: 2.3.1.8.5
>>
>> That's where I find them as well, so I don't know where Ken got his
>> annotation ... perhaps 3.6 but hey that's ancient history right? It's
>> usually more meaningful to say ... e.g: in the Reference 3.1.8.5
>>
>> As far as the content at Reference 3.1.8.5 ... user defined functions is
>> an advanced technique. If you've gotten that far there does seem to be a
>> build in assumption ... not that big of a leap IMHO.
>
> In the 3.7 RC6 help file that opens up for me it is section 3.2.1.6.5
> I suppose I should be installing RC7.

apologies Ken ... history but not so ancient ;-)

Post a reply to this message

On 02/27/2013 12:43 PM, James Holsenback wrote:
> On 02/27/2013 10:04 AM, Trevor G Quayle wrote:
>> James Holsenback <nom### [at] nonecom> wrote:
>>> On 02/27/2013 07:39 AM, Thomas de Groot wrote:
>>>> On 27-2-2013 10:34, Kenneth wrote:
>>>>> 3.2.1.6.5  "Declaring User-Defined Color Functions".
>>>>
>>>> A bit difficult to find ;-)
>>>>
>>>> in the 3.7 RC7 offline Docs: 3.3.1.8.5
>>>> in the online wiki Docs: 2.3.1.8.5
>>>
>>> That's where I find them as well, so I don't know where Ken got his
>>> annotation ... perhaps 3.6 but hey that's ancient history right? It's
>>> usually more meaningful to say ... e.g: in the Reference 3.1.8.5
>>>
>>> As far as the content at Reference 3.1.8.5 ... user defined functions is
>>> an advanced technique. If you've gotten that far there does seem to be a
>>> build in assumption ... not that big of a leap IMHO.
>>
>> In the 3.7 RC6 help file that opens up for me it is section 3.2.1.6.5
>> I suppose I should be installing RC7.
>
> apologies Ken ... history but not so ancient ;-)
>

Oh and if you guys haven't already noticed the Reference has undergone a 
bit of a re-organization

Post a reply to this message

James Holsenback <nom### [at] nonecom> wrote:
> On 02/27/2013 12:43 PM, James Holsenback wrote:
> Oh and if you guys haven't already noticed the Reference has undergone a
> bit of a re-organization

Is there a reason for the reorganization?  Usually reference standards try to
preserve their organization and clause numbering where possible to maintain
continuity.  Certainly people using the newest version can use the new reference
and be followed, however, if people are reading back at old postings on various
topics, it can cause some confusion.

-tgq

Post a reply to this message

On 27/02/2013 4:14 PM, Warp wrote:
> Kenneth <kdw### [at] gmailcom> wrote:
>> Here are the two code lines given there:
>
>> #declare Vec = foo(1,2,3)
>
>> and
>
>> #declare Val = foo(2,3,4).gray
>
>> What do the values (1,2,3) and (2,3,4) represent?
>
> They mean whatever the function wants them to mean. The function
> constructs the vector from those values.
>

Do you mean that you could write:

#declare Vec = foo(A,B,C)
#declare Val = foo(X,Y,Z).gray
or
#declare Val = foo(1,2,3).gray
even

And that would the same as writing:

#declare Vec = foo(1,2,3)
#declare Val = foo(2,3,4).gray
?

-- 
Regards
     Stephen

Post a reply to this message