Attributes: add .data_readonly field to attributes in RNA #112150
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Reference: blender/blender#112150
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Python can change attributes via the attribute RNA API (
rna_attribute.cc
). The issue is that we can't differentiate between read-only access and modifications when retrieving an attribute array. For that reason, we have to make attribute arrays unique (aka potentially copy them) whenever they are accessed via Python/RNA, because they might be modified (#111514). This is inefficient.A solution is to introduce
Attribute.data_readonly
next to the existingAttribute.data
, which does not allow modifying the underlying data. Script authors can optimize their code by using this instead of.data
.Internally, in C++, the API works the other way around. By default, things are read-only, but one can use a
*_for_write
function to gain write access. This is generally better, but we don't do that here, because it would break the existing API and it's more typical that everything is mutable in Python and the Blender API.this will restore our ability to use a modal operator to interact with sim data?
Ideasman42 said to list any fix I may have here.
Could we have some middle ground?
perhaps the depsgraph update_tag() is currently not used in evaluated meshes
we can have this set as false when passed to a object
when set true it adds objects to a list to update using depsgraph
if the value stays false we don't sync up the mesh
or perhaps a function python can use to set original data that geometry nodes does not have access to?