The simulation state used by simulation nodes is owned by the modifier. Since a
geometry nodes setup can contain an arbitrary number of simulations, the modifier
has a mapping from `SimulationZoneID` to `SimulationZoneState`. This patch changes
what is used as `SimulationZoneID`.
Previously, the `SimulationZoneID` contained a list of `bNode::identifier` that described
the path from the root node tree to the simulation output node. This works ok in many
cases, but also has a significant problem: The `SimulationZoneID` changes when moving
the simulation zone into or out of a node group. This implies that any of these operations
loses the mapping from zone to simulation state, invalidating the cache or even baked data.
The goal of this patch is to introduce a single-integer ID that identifies a (nested) simulation
zone and is stable even when grouping and un-grouping. The ID should be stable even if the
node group containing the (nested) simulation zone is in a separate linked .blend file and
that linked file is changed.
In the future, the same kind of ID can be used to store e.g. checkpoint/baked/frozen data
in the modifier.
To achieve the described goal, node trees can now store an arbitrary number of nested node
references (an array of `bNestedNodeRef`). Each nested node reference has an ID that is
unique within the current node tree. The node tree does not store the entire path to the
nested node. Instead it only know which group node the nested node is in, and what the
nested node ID of the node is within that group. Grouping and un-grouping operations
have to update the nested node references to keep the IDs stable. Importantly though,
these operations only have to care about the two node groups that are affected. IDs in
higher level node groups remain unchanged by design.
A consequence of this design is that every `bNodeTree` now has a `bNestedNodeRef`
for every (nested) simulation zone. Two instances of the same simulation zone (because
a node group is reused) are referenced by two separate `bNestedNodeRef`. This is
important to keep in mind, because it also means that this solution doesn't scale well if
we wanted to use it to keep stable references to *all* nested nodes. I can't think of a
solution that fulfills the described requirements but scales better with more nodes. For
that reason, this solution should only be used when we want to store data for each
referenced nested node at the top level (like we do for simulations).
This is not a replacement for `ViewerPath` which can store a path to data in a node tree
without changing the node tree. Also `ViewerPath` can contain information like the loop
iteration that should be viewed (#109164). `bNestedNodeRef` can't differentiate between
different iterations of a loop. This also means that simulations can't be used inside of a
loop (loops inside of a simulation work fine though).
When baking, the new stable ID is now written to disk, which means that baked data is
not invalidated by grouping/un-grouping operations. Backward compatibility for baked
data is provided, but only works as long as the simulation zone has not been moved to
a different node group yet. Forward compatibility for the baked data is not provided
(so older versions can't load the data baked with a newer version of Blender).
Pull Request: https://projects.blender.org/blender/blender/pulls/109444
Add a quaternion attribute type that will be used in combination with
rotation sockets for geometry nodes to give a more intuitive experience
and better performance when using rotations.
The most interesting part is probably the interpolation, the rest is
the same as the last attribute type addition, 988f23cec3.
We need to interpolate multiple values with different weights.
Based on Sybren's suggestion, this uses the `expmap` methods from
4805a54525 for that.
This also refactors `SimpleMixerWithAccumulationType` to use a
function rather than a cast to convert to the accumulation type.
See #92967
Pull Request: https://projects.blender.org/blender/blender/pulls/108678
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/
This adds `char *simulation_bake_directory` to the nodes modifier. The path is automatically generated the first time the modifier is baked. It is _not_ automatically changed afterwards. The path is relative to the .blend file by default. For now, the path is not exposed in the UI or Python API.
This fixes issues where renaming objects/modifiers can cause the baked data to not work anymore.
Pull Request: https://projects.blender.org/blender/blender/pulls/108201
This adds support for building simulations with geometry nodes. A new
`Simulation Input` and `Simulation Output` node allow maintaining a
simulation state across multiple frames. Together these two nodes form
a `simulation zone` which contains all the nodes that update the simulation
state from one frame to the next.
A new simulation zone can be added via the menu
(`Simulation > Simulation Zone`) or with the node add search.
The simulation state contains a geometry by default. However, it is possible
to add multiple geometry sockets as well as other socket types. Currently,
field inputs are evaluated and stored for the preceding geometry socket in
the order that the sockets are shown. Simulation state items can be added
by linking one of the empty sockets to something else. In the sidebar, there
is a new panel that allows adding, removing and reordering these sockets.
The simulation nodes behave as follows:
* On the first frame, the inputs of the `Simulation Input` node are evaluated
to initialize the simulation state. In later frames these sockets are not
evaluated anymore. The `Delta Time` at the first frame is zero, but the
simulation zone is still evaluated.
* On every next frame, the `Simulation Input` node outputs the simulation
state of the previous frame. Nodes in the simulation zone can edit that
data in arbitrary ways, also taking into account the `Delta Time`. The new
simulation state has to be passed to the `Simulation Output` node where it
is cached and forwarded.
* On a frame that is already cached or baked, the nodes in the simulation
zone are not evaluated, because the `Simulation Output` node can return
the previously cached data directly.
It is not allowed to connect sockets from inside the simulation zone to the
outside without going through the `Simulation Output` node. This is a necessary
restriction to make caching and sub-frame interpolation work. Links can go into
the simulation zone without problems though.
Anonymous attributes are not propagated by the simulation nodes unless they
are explicitly stored in the simulation state. This is unfortunate, but
currently there is no practical and reliable alternative. The core problem
is detecting which anonymous attributes will be required for the simulation
and afterwards. While we can detect this for the current evaluation, we can't
look into the future in time to see what data will be necessary. We intend to
make it easier to explicitly pass data through a simulation in the future,
even if the simulation is in a nested node group.
There is a new `Simulation Nodes` panel in the physics tab in the properties
editor. It allows baking all simulation zones on the selected objects. The
baking options are intentially kept at a minimum for this MVP. More features
for simulation baking as well as baking in general can be expected to be added
separately.
All baked data is stored on disk in a folder next to the .blend file. #106937
describes how baking is implemented in more detail. Volumes can not be baked
yet and materials are lost during baking for now. Packing the baked data into
the .blend file is not yet supported.
The timeline indicates which frames are currently cached, baked or cached but
invalidated by user-changes.
Simulation input and output nodes are internally linked together by their
`bNode.identifier` which stays the same even if the node name changes. They
are generally added and removed together. However, there are still cases where
"dangling" simulation nodes can be created currently. Those generally don't
cause harm, but would be nice to avoid this in more cases in the future.
Co-authored-by: Hans Goudey <h.goudey@me.com>
Co-authored-by: Lukas Tönne <lukas@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/104924
