POV-Ray : Newsgroups : povray.general : image_map memory use-- question : Re: image_map memory use-- question Server Time
29 Jul 2021 20:46:36 EDT (-0400)
  Re: image_map memory use-- question  
From: clipka
Date: 12 Jul 2021 02:09:21
Message: <60ebdc91$1@news.povray.org>
Am 12.07.2021 um 01:34 schrieb Kenneth:
> Is there a way to 'undefine' an image_map, once it has been loaded into memory
> during the parsing of a scene? So that its memory is 'released'? AFAIU, using
> #undef simply undefines the *identifier* for the image (not the image_map
> itself), which is not what I'm talking about.

As a general rule of thumb, whenever you "discard" an identifier's value 
(because you `#undef` it, assign a new value, re-define it as a macro, 
or whatever), any associated memory will automatically be released IF 
there doesn't exist another reference to that data.

Additional references will typically be created when you:

- assign the value to another variable, or
- "attach" the value to some other scene element, e.g. use an 
image-based pigment in an object.

Simply evaluating an image-based pigment will not create an additional 
reference.


There are a few exceptions to this:
- Some data will always be copied, rather than additional references 
created; and
- Some data will be cached because it is expected to re-occur later, and 
is sufficiently complicated to process that it would be a waste to do it 
all over again.

An example for the latter would be font files, which aren't discarded 
even when a `text` object is discarded, because POV-Ray anticipates that 
you might use the same font (and possibly also some of the characters) 
in other `text` objects.

POV-Ray doesn't cache image files, so you should be fine with what 
you're trying to do, even without any extra precautions.


TL;DR:

> Is the efficient way to do this simply a matter of re-#declaring each 'new'
> image with the *same* identifier? (Assuming a proper-size array has already been
> pre-#declared to hold the eval_pigment results):

Yup.


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