This was essentially a use-after-free issue. When a geometry nodes
group changes it has to be preprocessed again before it can be evaluated.
This part was working, the issue was that parent node groups have to be
preprocessed as well, which was missing. The lazy-function graph cached
on the parent node group was still referencing data that was freed when
the child group changed.
Now the depsgraph makes sure that all relevant geometry node groups are
preprocessed again after a change.
This issue was found by Simon Thommes.
This refactors the geometry nodes evaluation system. No changes for the
user are expected. At a high level the goals are:
* Support using geometry nodes outside of the geometry nodes modifier.
* Support using the evaluator infrastructure for other purposes like field evaluation.
* Support more nodes, especially when many of them are disabled behind switch nodes.
* Support doing preprocessing on node groups.
For more details see T98492.
There are fairly detailed comments in the code, but here is a high level overview
for how it works now:
* There is a new "lazy-function" system. It is similar in spirit to the multi-function
system but with different goals. Instead of optimizing throughput for highly
parallelizable work, this system is designed to compute only the data that is actually
necessary. What data is necessary can be determined dynamically during evaluation.
Many lazy-functions can be composed in a graph to form a new lazy-function, which can
again be used in a graph etc.
* Each geometry node group is converted into a lazy-function graph prior to evaluation.
To evaluate geometry nodes, one then just has to evaluate that graph. Node groups are
no longer inlined into their parents.
Next steps for the evaluation system is to reduce the use of threads in some situations
to avoid overhead. Many small node groups don't benefit from multi-threading at all.
This is much easier to do now because not everything has to be inlined in one huge
node tree anymore.
Differential Revision: https://developer.blender.org/D15914
The purpose of `NodeTreeRef` was to speed up various queries on a read-only
`bNodeTree`. Not that we have runtime data in nodes and sockets, we can also
store the result of some queries there. This has some benefits:
* No need for a read-only separate node tree data structure which increased
complexity.
* Makes it easier to reuse cached queries in more parts of Blender that can
benefit from it.
A downside is that we loose some type safety that we got by having different
types for input and output sockets, as well as internal and non-internal links.
This patch also refactors `DerivedNodeTree` so that it does not use
`NodeTreeRef` anymore, but uses `bNodeTree` directly instead.
To provide a convenient API (that is also close to what `NodeTreeRef` has), a
new approach is implemented: `bNodeTree`, `bNode`, `bNodeSocket` and `bNodeLink`
now have C++ methods declared in `DNA_node_types.h` which are implemented in
`BKE_node_runtime.hh`. To make this work, `makesdna` now skips c++ sections when
parsing dna header files.
No user visible changes are expected.
Differential Revision: https://developer.blender.org/D15491
