[Bf-python] Fastest way for RenderEngine to return combined rgba + z

[Brecht Van Lommel]

Hi,

On Thu, Jan 31, 2013 at 11:36 PM, Asbjørn <lordcrc at gmail.com> wrote:
> This method is very slow. It seems the overhead of converting the
> internal data to lists is quite high. Returning an iterator for the
> outer list of rgba pixels did not improve the situation noticeably.
>
> Are there better (API) ways of doing this directly, that is, without
> loading files from disk?

I think currently loading from disk is still the quickest method,
especially as on a modern OS the contents of that file is cached in
memory on doesn't actually have to be read from the physical disk
usually.

We could implement a more efficient way to assign the pixels though by
letting it accept a buffer object, which you could then use to wrap
the pixels without actually having to copy them into a python list.
http://docs.python.org/3.3/c-api/buffer.html

There is already a trick that you can use, it didn't work entirely
before but I just committed a fix for that. Basically you use the
foreach_set method which accepts a buffer object:
http://www.blender.org/documentation/blender_python_api_2_65_9/bpy.types.bpy_prop_collection.html?highlight=foreach_get#bpy.types.bpy_prop_collection.foreach_set

Example here. The inconvenient thing about this is you have to set the
pixels for all layers/passes at once, but it should be quick if the
lux C code can create the python buffer object.
http://www.pasteall.org/39345/python

Brecht.