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From: Mr
Subject: Re: Reviving some pov4 discussion
Date: 17 Sep 2015 04:30:01
Message: <web.55fa79128cd067d516086ed00@news.povray.org>
"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> clipka <ano### [at] anonymousorg> wrote:
> > Am 04.08.2015 um 16:10 schrieb Warp:
> > > clipka <ano### [at] anonymousorg> wrote:
> > >> Note that my goal is for the language /per se/ to have a very simple
> > >> syntax, and make it pretty much oblivious to rendering, except for
> > >> providing a few special native data types like 3D vectors and colours.
> > >> It'll be up to a bunch of predefined classes to fill it with raytracing
> > >> life in its scene description role. Such a language should be generic
> > >> enough to also be suited for the shader description role, so it would be
> > >> rather pointless and user-unfriendly to devise yet another language for
> > >> that purpose.
> > >
> > > OTOH the "shader" part has to, by necessity, be more limited than the
> > > generic part of the language. It wouldn't make sense, for example, to
> > > be able to create new objects into the scene while evaluating, for
> > > example, the color of a reflected ray. That would mess up things quite
> > > badly, I think.
> >
> > That's part of the "fill it with raytracing life" thing: To add geometry
> > to the scene, you'd invoke particular classes (such as a "sphere" class,
> > a "box" class, and so on), which just won't be available in shaders.
>
> why not simply add a shader option to the texture block, and use something like
> OSL for the shader language?
>
> http://code.google.com/p/openshadinglanguage/
>
> Regards,
> A.D.B.


As a beginner, When I considered options of free renderers to learn, I chose
POV-Ray over Aqsis and other RIB like alternatives. One of the reasons was that
it had one language to learn instead of two, and this also felt a relief later
when deciding to script for an exporter, which had to be written in yet another
language (Python) (by the way Mitsuba has a full Python API/SDL which makes it
very attractive in this regard but it does miss a lot of the POV-Ray features)

Also I get the point that externalizing development by relying on solid
standards like the OSL you suggest allows developers to focus on more important
things, but the SDL is really central and one of the biggest selling point of
POV-Ray. It made me chose it not because it was standard, but because I trusted
it had the potential to be better than standard.


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From: Mike Horvath
Subject: Re: Reviving some pov4 discussion
Date: 10 Dec 2015 19:20:33
Message: <566a16d1$1@news.povray.org>
On 7/30/2015 6:15 AM, Warp wrote:
> Some of these are things I have discussed years ago, but I thought it
> could be useful to revive the discussion a bit.
>
> One of the original plans for POV-Ray 4 was to make a complete rehaul
> of the SDL from scratch, making it a lot more versatilve, expressive,
> powerful and faster (via byte-compilation). This would have been a
> completely new input language that's different from the current one
> (but with, perhaps, a backwards compatibility mode to support existing
> scene files.)

I think basing things of SVG would be a good idea. I.e. XML + SMIL + 
JavaScript.


Mike


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From: clipka
Subject: Re: Reviving some pov4 discussion
Date: 11 Dec 2015 10:04:05
Message: <566ae5e5$1@news.povray.org>
Am 11.12.2015 um 01:20 schrieb Mike Horvath:
> On 7/30/2015 6:15 AM, Warp wrote:
>> Some of these are things I have discussed years ago, but I thought it
>> could be useful to revive the discussion a bit.
>>
>> One of the original plans for POV-Ray 4 was to make a complete rehaul
>> of the SDL from scratch, making it a lot more versatilve, expressive,
>> powerful and faster (via byte-compilation). This would have been a
>> completely new input language that's different from the current one
>> (but with, perhaps, a backwards compatibility mode to support existing
>> scene files.)
> 
> I think basing things of SVG would be a good idea. I.e. XML + SMIL +
> JavaScript.

Abso-bloody-lutely not.

XML is quite useful for the static description of purely hierarchical
structures comprised mainly of textual information; for anything else,
it is overly verbose and/or excessively difficult to employ.

A POV-Ray scene is indeed, in essence, a description of purely
hierarchical structures; however, that's where the applicability of XML
ends:

- The information in a POV-Ray scene is mostly non-textual, which means
that much of the overhead XML introduces is entirely unnecessary (such
as the enclosing of tags in angular brackets, or of attribute values in
double quotes).

- POV-Ray's current SDL excels (arguably not in speed, but certainly in
flexibility) in the dynamic generation of scenes; its description of
information is non-static, and a successor to its SDL should indeed
provide the same feature with similar ease. XML is poorly suited for
that: XML-based notations for control structures tend to be excessively
complicated.

The grafting of JavaScript on top of XML (or, more precisely, into its
bowels) does provide a way of generating information dynamically with
more ease than XML alone would allow; however, this is nothing more than
a makeshift solution -- one that has caught on, I give you that, but
that doesn't mean it's anywhere close to elegant: You do need to learn
two entirely different languages, XML and JavaScript.

In fact, the fusing of XML and JavaScript is as ugly a chimera as it can
possibly get: Some valid (and in fact pretty much essential) JavaScript
operators are invalid as XML content; as a matter of fact, /all/
characters that are invalid in XML content may occur as operators in
JavaScript. Thus, embedding arbitrary JavaScript into XML is only
possible via a workaround that hijacks XML comments - which should
normally be ignored - to contain relevant content. And even then, it is
possible to write JavaScript code snippets that break the mechanism by
which they are embedded into XML.

The only clean solution to this problem is to let the JavaScript
portions reside in entirely different files; but that defies the whole
purpose of having a unified language to describe content in a dynamic
fashion.


When it comes to data exchange formats, rather than XML, a much more
suitable candidate for a future POV-Ray SDL would be JSON. But even
then, I think it should only serve as a source for inspiration, rather
than being employed "out of the box".


In my opinion it remains a fact that the best language for POV-Ray would
be a domain-specific language (and by that I don't mean a
domain-specific abuse of an existing language like Apache Camel's DSL,
but a genuine language in its own right).


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From: Dick Balaska
Subject: Re: Reviving some pov4 discussion
Date: 11 Dec 2015 11:43:18
Message: <MPG.30d4c73419c41bdd98968e@news.povray.org>
In article <566ae5e5$1@news.povray.org>, ano### [at] anonymousorg says...
> > I think basing things of SVG would be a good idea. I.e. XML + SMIL +
> > JavaScript.
> 
> Abso-bloody-lutely not.

I thought the same thing. XML is a bitch to write by hand. Awesome for 
machine generation, though.

> You do need to learn
> two entirely different languages, XML and JavaScript.

Yeah, but povray is two fused languages now.  The DKBTrace "C" type of 
object definition (which I learned first...) and a perl-ish procedural 
language bolted on top of that.

I thought of JSON when he said XML, but is that really any better than 
what exists? It just replaces the current braces with brackets and 
braces.  One advantage might be, my only complaint about the current 
language is the inconsistent use of semicolons and commas.
#declare SemicolonRequired=1;
#debug "no semicolon here\n"
torus { 1, 0.1 }	// comma please
cone { <0,0,0> 1 <1,1,1> 2 }	// 4 params no commas

dik


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From: Le Forgeron
Subject: Re: Reviving some pov4 discussion
Date: 11 Dec 2015 16:37:32
Message: <566b421c$1@news.povray.org>
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Le 11/12/2015 17:43, Dick Balaska a écrit :
> In article <566ae5e5$1@news.povray.org>, ano### [at] anonymousorg
> says...
>>> I think basing things of SVG would be a good idea. I.e. XML +
>>> SMIL + JavaScript.
>> 
>> Abso-bloody-lutely not.
> 
> I thought the same thing. XML is a bitch to write by hand. Awesome
> for machine generation, though.

writing once xml is not a problem... it's reading it later and trying
to amend it that is really painful.

> 
>> You do need to learn two entirely different languages, XML and
>> JavaScript.
> 
> Yeah, but povray is two fused languages now.  The DKBTrace "C" type
> of object definition (which I learned first...) and a perl-ish
> procedural language bolted on top of that.
> 
> I thought of JSON when he said XML, but is that really any better
> than what exists? It just replaces the current braces with brackets
> and braces.  One advantage might be, my only complaint about the
> current language is the inconsistent use of semicolons and commas. 
> #declare SemicolonRequired=1; #debug "no semicolon here\n" torus {
> 1, 0.1 }	// comma please cone { <0,0,0> 1 <1,1,1> 2 }	// 4 params
> no commas
> 
> dik
> 

If I was crazy, I would use C++ and a compiler as the parser, filling
a scene object with other objects... a rendering would be the
interaction of a camera with a scene. The only problem I would
foresee: the dynamic generation of code ... you know, the first part
of the parsing generate an include file to be included later... but do
we really need that ?(I'm afraid someone will want it).

Animation ? well, just a matter of looping...

Povray 3D objects, and all others aspects, just a library within a
dedicated namespace.

usual functions : just native coding.

Remaining problem: new users have to learn C++ and get a C++ compiler,
linking with the povray library.

Povray::Torus obj1(1,0.1);
// texturing can be a post constructor operation
Povray::Cone obj2( Povray::3DVector(0,0,0), 1, Povray::3DVector(), 2);
Povray::Scene take1;
take1 += obj1;
take1 += obj2;

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From: clipka
Subject: Re: Reviving some pov4 discussion
Date: 11 Dec 2015 18:32:53
Message: <566b5d25@news.povray.org>
Am 11.12.2015 um 22:37 schrieb Le_Forgeron:

> If I was crazy, I would use C++ and a compiler as the parser, filling
> a scene object with other objects...

> Povray::Torus obj1(1,0.1);
> // texturing can be a post constructor operation
> Povray::Cone obj2( Povray::3DVector(0,0,0), 1, Povray::3DVector(), 2);

Still unnecessarily complex, as compared to (e.g.)

cone { <0,0,0>, <0,1,0>, 2 }


One of the key properties of a POV-Ray scene, which make the
requirements for the future SDL so unique, is that it may contain (A)
descriptions of complex algorithms as well as (B) descriptions of
hierarchical data, mixed arbitrarily.

XML, JSON & co. are useful for (B) but cumbersome for (A), while classic
programming languages excel at (A) but suck at (B).

(Add to this the fact that POV-Ray makes heavy use of vectors and
colours, which in most programming languages would have to be "bolted
on" artificially, which usually makes for less than ideal syntax.)


I re-iterate: The ideal SDL for POV-Ray has yet to be designed.

(POV-Ray 3.x SDL manages to cater to both requirements comparatively
well, but - as Dick correctly points out - sucks big time in terms of
consistency; also, it's somewhat outdated when it comes to describing
algorithms efficiently.)

I'm not writing this to crush people's hope for a new SDL; rather to the
contrary, I'd say. But I'd love to crush the hope of any language's
fanboys that their favorite language may become that new SDL, or even
form the basis of it, and -- maybe more importantly -- direct people
away from the (almost inevitably) fruitless search for an ideal existing
language, towards actually contributing to the task of defining a new
language from scratch (drawing some inspiration from other languages
where it seems fitting, but leaving well-trodden paths where they would
be inefficient).


One possible way of contributing to this process would be to simply
write down some hypothetical scene in whatever format you think a
next-generation POV-Ray SDL could look like. Some added text explaining
how that file format is structured would be nice to have, but could also
be deferred as a next step.


Remember, the format _must_:

- be efficient at describing static portions of a scene;

- be efficient at describing algorithms to construct portions of a scene
dynamically.

- be describing a scene in terms of essentially the same elements and
hierarchical structures as the current POV-Ray SDL (some individual
cleanup allowed, my favorite candidates there being the finish and
camera blocks);


As additional requirements, the format _must_:

- allow for two-step parsing, with the first step transforming the
verbose human-readable format into some kind of bytecode "program" that
is to be "executed" later by a virtual machine embedded into POV-Ray;
most notably this will prohibit "macros" from constructing only partial
statements, and dynamical generation of additional algorithmic portions
at execution time will probably be unavailable as well. (The idea behind
this requirement is to maximize parsing performance for scenes with
complex algorithms; the current plan calls for LLVM as the bytecode
format, allowing to even use just-in-time compilation of the scene file.)

- in its essential syntax be agnostic of the details of a scene's
elements and their hierarchy; e.g. the basic syntax must be unaware of
the fact that the element "texture" has a child element named "finish",
and instead only deal with the general fact that some elements have
child elements with specific names. (The idea behind this requirement is
manifold, from simplifying the parser to automatically enforcing more
consistency in the syntax, and even extending the exact same syntax to
user-defined elements.)


Also, the format _should_:

- support vectors and colours as native data types.

- provide some syntax to define custom geometric primitives, shading
models, and similar stuff.


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From: Mike Horvath
Subject: Re: Reviving some pov4 discussion
Date: 11 Dec 2015 23:54:29
Message: <566ba885@news.povray.org>
On 12/11/2015 6:32 PM, clipka wrote:
> One of the key properties of a POV-Ray scene, which make the
> requirements for the future SDL so unique, is that it may contain (A)
> descriptions of complex algorithms as well as (B) descriptions of
> hierarchical data, mixed arbitrarily.

One of the key properties that makes POV SDL great, but also one of the 
key properties that makes it unsupported by anyone else in the universe.

I don't like typing XML either but it might mean more third party tools 
in the future.


Mike


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From: Le Forgeron
Subject: Re: Reviving some pov4 discussion
Date: 12 Dec 2015 03:32:02
Message: <566bdb82$1@news.povray.org>
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Le 12/12/2015 00:32, clipka a écrit :
> Am 11.12.2015 um 22:37 schrieb Le_Forgeron:
> 
>> If I was crazy, I would use C++ and a compiler as the parser,
>> filling a scene object with other objects...
> 
>> Povray::Torus obj1(1,0.1); // texturing can be a post constructor
>> operation Povray::Cone obj2( Povray::3DVector(0,0,0), 1,
>> Povray::3DVector(), 2);
> 
> Still unnecessarily complex, as compared to (e.g.)
> 
> cone { <0,0,0>, <0,1,0>, 2 }
> 

Please notice, I wrote "If I was crazy".

of course C++11/14/17 could be abused with initialiser list in
constructor for:

scene += Cone( {0,0,0},{0,1,0}, 2);

that is just a matter of supported syntax for any language, I took
C++, but it would be the same with any other.
> 
> One of the key properties of a POV-Ray scene, which make the 
> requirements for the future SDL so unique, is that it may contain
> (A) descriptions of complex algorithms as well as (B) descriptions
> of hierarchical data, mixed arbitrarily.

[cutting the very good list of expectations]

Just beware of the NIH syndrome.
As well as over-generalisation (e.g. let make a super-generic system
to handle unthinkable evolutions), that's how you finish with heavy
XML inside SQL database, with mandatory manual joint using regular
expression applied on the single table of 2 or 3 columns, instead of
unfolding the whole data scheme across multiple dedicated tables (but
yes, a data scheme does not evolves to handle any extension, and due
to lack of initial strict requirements, you have a meta-engine instead
of a dedicated engine... so customers can customize it as they want...
well, there is no customer which are ready to pay for a meta-engine
and then pay again the customisation... excepted in the ERP/SAP
business model (or is it a mafia ?)).

Despite the C-like origin of SDL (or pascal... or whatever was fancy
in the 80's ), Povray is very object oriented.

Do we want to look at it like an interpreted or a compiled language,
it might be irrelevant for the speed, but in the approach provided to
the new users.
Do we want to write our own parser, or can it be left to an existing one
 ?

If it was one of boost library, would it still be povray ?


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From: clipka
Subject: Re: Reviving some pov4 discussion
Date: 12 Dec 2015 06:22:40
Message: <566c0380$1@news.povray.org>
Am 12.12.2015 um 05:54 schrieb Mike Horvath:
> On 12/11/2015 6:32 PM, clipka wrote:
>> One of the key properties of a POV-Ray scene, which make the
>> requirements for the future SDL so unique, is that it may contain (A)
>> descriptions of complex algorithms as well as (B) descriptions of
>> hierarchical data, mixed arbitrarily.
> 
> One of the key properties that makes POV SDL great, but also one of the
> key properties that makes it unsupported by anyone else in the universe.

Actually that is only true when it comes to /import/ of POV-Ray scenes
into other software. As far as /export/ is concerned, I think the key
properties that make it unsupported by popular 3D software are that (a)
they're all entirely mesh-based, while POV-Ray isn't, and (b) work on
POV-Ray appeared to have stalled for a decade or so after the last 3.6
release.

As a matter of fact, outside the mesh-based world, POV-Ray is still
comparatively popular as an export format.

> I don't like typing XML either but it might mean more third party tools
> in the future.

Choosing XML as the basis for an SDL would (or should) not change the
aforementioned key property of a POV-Ray scene, the mixing of static
data and algorithms, which you claim to be in the way of broader support.

One road I would be willing to go along would be to define a static XML-
(or better yet JSON-) based format, devoid of any scripting elements,
intended solely for efficient data exchange with other programs, to be
supported for input as an /alternative/ to the official SDL intended for
manual editing; also, one mode of operation for POV-Ray could be to not
actually render a scene, but rather to just convert it to that data
exchange format, effectively constituting data export.

Also, for improved integration into the mesh-based world, I think
winning features would be (A) inbuilt support for .obj as a mesh input
format, and (B) inbuilt support for tesselation and .obj export.

Another way to improve support from 3rd party tools could be to provide
the parser and tesselation code as library modules, to serve as a basis
for 3rd party tool import modules.


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From: clipka
Subject: Re: Reviving some pov4 discussion
Date: 12 Dec 2015 07:27:29
Message: <566c12b1$1@news.povray.org>
Am 12.12.2015 um 09:32 schrieb Le_Forgeron:

> [cutting the very good list of expectations]
> 
> Just beware of the NIH syndrome.

There's really nothing to beware there; if I could find a language out
there that does suit POV-Ray's needs, I'd probably be the first to go
for it; if nothing else, it would save us all the work of defining the
new SDL in the first place; a pre-existing parser to just plug into
POV-Ray would save a lot of work, too.

Also, if a few modifications to an existing language would get us there
(e.g. bolting some additional syntax for vector and colour data types to
the language), that's what I'd do.

But I won't sacrifice what I consider essential requirements, just to be
able to re-use existing components.


> Do we want to look at it like an interpreted or a compiled language,
> it might be irrelevant for the speed, but in the approach provided to
> the new users.

"We" as the developers definitely want to look /at it/ like a compiled
language, because that's what will give us the best performance in the
parsing of complex scenes.

As for whether the language is to /look like/ an interpreted or compiled
language to the user, you tell me what the difference is and I tell you
what we want. Except for dynamic creation of executable code at
execution time, I can think of nothing that would clearly delineate
interpreted languages from compiled ones.

If you ask whether we want a strongly or weakly typed language, then I'd
say that we want the language to generally be weakly typed, because
that's easier to use; but we probably also want strongly typed elements,
so that we get an early failure if someone mistypes a property name of
e.g. a geometric primitive, or tries to use e.g. a geometric primitive
where a texture is expected.

> Do we want to write our own parser, or can it be left to an existing one
>  ?

We certainly don't /want/ to write our own parser, because we have
enough other work to do, but if we have to (because the language does
not exist yet, or there's no open source parser for it yet, or no
embedded parser targeting an existing portable VM, or none that is
modular enough to be used as such), that's what we /will/ do out of
necessity.


> If it was one of boost library, would it still be povray ?

If boost contained a library providing a suitable embedded language, I'm
sure we'd already be halfway through integrating it into POV-Ray.


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