In order to address feedback that the "Stable ID" was not easy enough
to use, remove the "Stable ID" output from the distribution node and
the input from the instance on points node. Instead, the nodes write
or read a builtin named attribute called `id`. In the future we may
add more attributes like `edge_id` and `face_id`.
The downside is that more behavior is invisible, which is les
expected now that most attributes are passed around with node links.
This behavior will have to be explained in the manual.
The random value node's "ID" input that had an implicit index input
is converted to a special implicit input that uses the `id` attribute
if possible, but otherwise defaults to the index. There is no way to
tell in the UI which it uses, except by knowing that rule and checking
in the spreadsheet for the id attribute.
Because it isn't always possible to create stable randomness, this
attribute does not always exist, and it will be possible to remove it
when we have the attribute remove node back, to improve performance.
Differential Revision: https://developer.blender.org/D12903
We do this in other nodes to reduce overhead of using the same node more
than once. I don't think it will make a difference with index nodes
currently, but at least it's consistent.
Previously, some multi-functions were allocated in a resource scope.
This was fine as long as the multi-functions were only needed during
the current evaluation of the node tree. However, now cases arise
that require the multi-functions to be alive after the modifier is finished.
For example, we want to evaluate fields created with geometry nodes
outside of geometry nodes.
To make this work, `std::shared_ptr` has to be used in a few more places.
Realistically, this shouldn't have a noticable impact on performance.
If this does become a bottleneck in the future, we can think about ways
to make this work without using `shared_ptr` for multi-functions that
are only used once.
Previously, a debug name had to be passed to all methods
that added a resource to the `ResourceScope`. The idea was
that this would make it easier to find certain bugs. In reality
I never found this to be useful, and it was mostly annoying.
The thing is, something that is in a resource scope never leaks
(unless the resource scope is not destructed of course).
Removing the name parameter makes the structure easier to use.
Instead of comparing the referenced field node by pointer,
compare the nodes directly instead. This is important
because different field nodes might be the same semantically.
Since fields were committed to master, socket inspection did
not work correctly for all socket types anymore. Now the same
functionality as before is back. Furthermore, fields that depend
on some input will now show the inputs in the socket inspection.
I added support for evaluating constant fields more immediately.
This has the benefit that the same constant field is not evaluated
more than once. It also helps with making the field independent
of the multi-functions that it uses. We might still want to change
the ownership handling for the multi-functions of nodes a bit,
but that can be done separately.
Differential Revision: https://developer.blender.org/D12444
This implements the initial core framework for fields and anonymous
attributes (also see T91274).
The new functionality is hidden behind the "Geometry Nodes Fields"
feature flag. When enabled in the user preferences, the following
new nodes become available: `Position`, `Index`, `Normal`,
`Set Position` and `Attribute Capture`.
Socket inspection has not been updated to work with fields yet.
Besides these changes at the user level, this patch contains the
ground work for:
* building and evaluating fields at run-time (`FN_fields.hh`) and
* creating and accessing anonymous attributes on geometry
(`BKE_anonymous_attribute.h`).
For evaluating fields we use a new so called multi-function procedure
(`FN_multi_function_procedure.hh`). It allows composing multi-functions
in arbitrary ways and supports efficient evaluation as is required by
fields. See `FN_multi_function_procedure.hh` for more details on how
this evaluation mechanism can be used.
A new `AttributeIDRef` has been added which allows handling named
and anonymous attributes in the same way in many places.
Hans and I worked on this patch together.
Differential Revision: https://developer.blender.org/D12414
