POV-Ray : Newsgroups : povray.general : Status of Moray? : Re: New SDL for POVRay Server Time
5 Jul 2025 14:07:21 EDT (-0400)
  Re: New SDL for POVRay  
From: Warp
Date: 9 Oct 2007 05:55:34
Message: <470b5016@news.povray.org>
Bruno Cabasson <bru### [at] alcatelaleniaspacefr> wrote:
> I think that leaving the responsability to handle these stacks of
> transformations to the programmer is dangerous and requires too much
> programming skills wrt the goal we intend to reach in terms of programming
> ease and accessibility.

  There's no more skill involved than in the current POV-Ray when you apply
a series of transformations to an object.
  There's no need for a stack. There's no need to revert transformations.
You simply apply a series of transformations to the object at each frame
(basically what you do with the current SDL, but without having to reparse
the object).

  I really can't understand what is the problem people are seeing here.
Could someone please explain to me this?

  Is it that some people seem to think that once you have applied a
texture to the object you can't transform the object without transforming
the texture too? Says who? Just because you can't do it in the current SDL
that doesn't mean it wouldn't be possible in the new one. Even in the
current SDL it's just a *syntactical* limitation. There's absolutely no
technical reason why there couldn't be a command like "apply this
transformation to the object but not its texture". It would simply be
a question of adding the proper syntax for it.

  Seemingly some people also think that if a transformation has been
applied, it's engraved in stone and cannot be removed anymore. Removing
all the transformations is just a question of resetting the transformation
matrix. Then you can re-apply all the transformations you want to the
object, making the modifications you want.

  (Granted, in the current POV-Ray implementation this would require a
bit more of work because certain transformations to certain objects are
"optimized away", for example by applying the transformation to some
object coordinate instead of applying it to the transformation matrix.
Thus such a transformation would indeed by "engraved in stone" and not
possible to revert.
  However, it's perfectly possible to change this system without removing
these optimizations. It's possible to apply all the transformations to
the transformation matrix of the object and then, after all the
transformations have been applied, just before starting the rendering,
it's possible to examine the transformation matrix for certain properties
and if these properties exist, they can be "optimized away" in the same
way as currently. For example, if the object is a sphere there exists a
translation component, the translation can be applied to the center
coordinate of the sphere and removed from the transformation matrix.)

> My point of view is that within a single frame, all transforms should be
> defined at creation time, and post creation transforms should be forbidden

  Why impose such an artificial limitation? It doesn't make any sense.

-- 
                                                          - Warp


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