This refactors how a geometry nodes node tree is converted to a lazy-function
graph. Previously, all nodes were inserted into a single graph. This was fine
because every node was evaluated at most once per node group evaluation.
However, loops (#108896) break this assumption since now nodes may be
evaluated multiple times and thus a single flat graph does not work anymore.
Now, a separate lazy-function is build for every zone which gives us much
more flexibility for what can happen in a zone. Right now, the change only
applies to simulation zones since that's the only kind of zone we have.
Technically, those zones could be inlined, but turning them into a separate
lazy-function also does not hurt and makes it possible to test this refactor
without implementing loops first. Also, having them as separate functions
might help in the future if we integrate a substep loop directly into the
simulation zone.
The most tricky part here is to just link everything up correctly, especially
with respect to deterministic anonymous attribute lifetimes. Fortunately,
correctness can be checked visually by looking at the generated graphs.
The logging/viewer system also had to be refactored a bit, because now there
can be multiple different `ComputeContext` in a single node tree. Each zone
is in a separate `ComputeContext`. To make it work, the `ViewerPath` system
now explicitly supports zones and drawing code will look up the right logger
for showing inspection data.
No functional changes are expected, except that the spreadsheet now shows
"Simulation Zone" in the context path if the viewer is in a simulation.
A lot of files were missing copyright field in the header and
the Blender Foundation contributed to them in a sense of bug
fixing and general maintenance.
This change makes it explicit that those files are at least
partially copyrighted by the Blender Foundation.
Note that this does not make it so the Blender Foundation is
the only holder of the copyright in those files, and developers
who do not have a signed contract with the foundation still
hold the copyright as well.
Another aspect of this change is using SPDX format for the
header. We already used it for the license specification,
and now we state it for the copyright as well, following the
FAQ:
https://reuse.software/faq/
Whenever a node group is entered during evaluation, a new compute
context is entered which has a corresponding hash. When node groups
are entered and exited a lot, this can have some overhead. In my test
file with ~100.000 node group invocations, this patch improves performance
by about 7%.
The speedup is achieved in two ways:
* Avoid computing the same hash twice by caching it.
* Invoke the hashing algorithm (md5 currently) only once instead of twice.
This patch adds an integer identifier to nodes that doesn't change when
the node name changes. This identifier can be used by different systems
to reference a node. This may be important to store caches and simulation
states per node, because otherwise those would always be invalidated
when a node name changes.
Additionally, this kind of identifier could make some things more efficient,
because with it an integer is enough to identify a node and one does not
have to store the node name.
I observed a 10% improvement in evaluation time in a file with an extreme
number of simple math nodes, due to reduced logging overhead-- from
0.226s to 0.205s.
Differential Revision: https://developer.blender.org/D15775
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
Jacques Lucke
Sergey Sharybin
Hans Goudey