Drivers: Introduce the Context Properties
The goal: allow accessing context dependent data, such as active scene camera
without linking to a specific scene data-block. This is useful in cases when,
for example, geometry node setup needs to be aware of the camera position.
A possible work-around without changes like this is to have some scene
evaluation hook which will update driver variables for the currently evaluating
scene. But this raises an issue of linking: it is undesirable that the asset
scene is linked to the shot file.
Surely, it is possible to have post-evaluation handler to clear the variables,
but it all starts to be quite messy. Not to mention possible threading
conflicts.
Another possibility of introducing a way to achieve the goal is to make it so
the dependency graph somehow parses the python expression where artists can
(and already are trying to) type something like:
depsgraph.scene.camera.matrix_world.col[3][0]
But this is not only tricky to implement properly and reliably, it hits two
limitations:
- Currently dependency graph can only easily resolve dependencies to a RNA
property.
- Some properties access which are valid in Python are not considered valid
RNA properties by the existing property resolution functions:
`camera.matrix_world[3][0]` is a valid RNA property, but
`camera.matrix_world.col[3][0]` is not.
Using driver variables allows to have visual feedback when the path resolution
fails, and there is no way to visualize errors in the python expression itself.
This change introduces the new variable type: Context Property. Using this
variable type makes allows to choose between Active Scene and Active View
Layer. These scene and view layer are resolved during the driver evaluation
time, based on the current dependency graph.
This allows to create a driver variable in the following configuration:
- Type: Context Property
- Context Property: Active Scene
- Path: camera.matrix_world[3][0]
The naming is a bit confusing. Tried my best to keep it clear keeping two
aspects in mind: using UI naming when possible, and follow the existing
naming.
A lot of the changes are related on making it so the required data is available
from the variable evaluation functions. It wasn't really clear what the data
would be, and the scope of the changes, so it is done together with the
functional changes.
It seems that there is some variable evaluation logic duplicated in the
`bpy_rna_driver.c`. This change does not change it. It is not really clear why
this separate code path with much more limited scope of supported target types
is even needed.
There is also a possible change in the behavior of the dependency graph: it
is now using ID of the resolved path when building driver variables. It used
to use the variable ID. In common cases they match, but when going into nested
data-blocks it is actually correct to use relation to the resolved ID. Not sure
if there was some code to ensure that, which now can be resolved. Also not sure
whether it is still needed to ensure the ID specified in the driver target is
build as well. Intuitively it is not needed.
Pull Request #105132
The following opcodes have been added, see [0] for details:
- LIST_TO_TUPLE: convert a list to a tuple,
use for constructing lists/tuples in some cases.
- LIST_EXTEND: use for constructing lists with unpacking.
- SET_UPDATE: use for constructing sets with unpacking.
- CONTAINS_OP: check if `a in b` generally useful.
When writing tests these op-codes where needed for basic operations
and can be safely supported.
Add note why dictionary manipulation op-codes have been left out.
Also restrict namsepace access to anything with an underscore prefix
since these may be undocumented.
[0]: https://docs.python.org/3.10/library/dis.html
Showing the expression alone may not be enough to track down an error
evaluating a py-driver. Show information about the target ID & property
in the error message as well.
Error in [0] which assumed the struct member was renamed however
byte-code access from PyCodeObject now requires an API call.
Thanks to @music for pointing this out.
[0]: 780c0ea097
- Use API calls to access frame-data as PyFrameObject is now opaque.
- Update opcodes allowed for safe driver evaluation.
**Details**
Some opcodes have been added for safe-driver evaluation.
Python 3.11 removes many opcodes - the number of accepted opcodes in
Blender's listing dropped from 65 to 43) however some new opcodes
also needed to be added. As this relates to security details about newly
added opcodes have been noted below (see [0] for full documentation).
Newly added opcodes:
- CACHE:
Used to control caching instructions.
- RESUME:
A no-op. Performs internal checks.
- BINARY_OP:
Implements the binary and in-place operators,
replacing specific binary operations.
- CALL, PRECALL, KW_NAMES:
Used for calling functions, replacing some existing opcodes.
- POP_JUMP_{FORWARD/BACKWARD}_IF_{TRUE/FALSE/NONE/NOT_NONE}.
Manipulate the byte-code counter.
- SWAP, PUSH_NULL.
Stack manipulation.
Resolves T99277.
[0]: https://docs.python.org/3.11/library/dis.html
New opcodes added since 3.7 meant some actions such as `len()`
were disabled in safe py-driver execution.
The following opcodes have been added, see [0] for details:
- ROT_FOUR: similar to existing ROT_* opcodes, added v3.8.
- ROT_N: similar to existing ROT_* opcodes, added v3.10.
- GET_LEN: Push len(TOS) onto the stack, added v3.10.
- IS_OP: for ternary operator, added v3.9.
- BUILD_SLICE: access `slice` built-in, doesn't expose new
functionality beyond existing `__getitem__` access.
[0]: https://docs.python.org/3.10/library/dis.html
So far it was needed to declare a new RNA struct to `RNA_access.h` manually.
Since 9b298cf3db we generate a `RNA_prototypes.h` for RNA property
declarations. Now this also includes the RNA struct declarations, so they don't
have to be added manually anymore.
Differential Revision: https://developer.blender.org/D13862
Reviewed by: brecht, campbellbarton
Avoid re-creating & freeing the depsgraph for every driver evaluation.
Now the depsgraph is kept in the name-space (matching self),
only re-created when the value changes.
In a contrived test-case with many drivers this gave ~15% overall
speedup for animation playback.
Use a shorter/simpler license convention, stops the header taking so
much space.
Follow the SPDX license specification: https://spdx.org/licenses
- C/C++/objc/objc++
- Python
- Shell Scripts
- CMake, GNUmakefile
While most of the source tree has been included
- `./extern/` was left out.
- `./intern/cycles` & `./intern/atomic` are also excluded because they
use different header conventions.
doc/license/SPDX-license-identifiers.txt has been added to list SPDX all
used identifiers.
See P2788 for the script that automated these edits.
Reviewed By: brecht, mont29, sergey
Ref D14069
Implementation of lerp without a function requires repeating one of
the arguments, which is not ideal. To avoid that, add a new function
to the driver namespace. In addition, provide a function for clamping
between 0 and 1 to support easy clamped lerp, and a smoothstep function
from GLSL that is somewhat related.
The function implementations are added to a new bl_math module.
As an aside, add the round function and two-argument log to the
pylike expression subset.
Differential Revision: https://developer.blender.org/D8205
Custom driver functions need access to the dependency graph that is
triggering the evaluation of the driver. This patch passes the
dependency graph pointer through all the animation-related calls.
Instead of passing the evaluation time to functions, the code now passes
an `AnimationEvalContext` pointer:
```
typedef struct AnimationEvalContext {
struct Depsgraph *const depsgraph;
const float eval_time;
} AnimationEvalContext;
```
These structs are read-only, meaning that the code cannot change the
evaluation time. Note that the `depsgraph` pointer itself is const, but
it points to a non-const depsgraph.
FCurves and Drivers can be evaluated at a different time than the
current scene time, for example when evaluating NLA strips. This means
that, even though the current time is stored in the dependency graph, we
need an explicit evaluation time.
There are two functions that allow creation of `AnimationEvalContext`
objects:
- `BKE_animsys_eval_context_construct(Depsgraph *depsgraph, float
eval_time)`, which creates a new context object from scratch, and
- `BKE_animsys_eval_context_construct_at(AnimationEvalContext
*anim_eval_context, float eval_time)`, which can be used to create a
`AnimationEvalContext` with the same depsgraph, but at a different
time. This makes it possible to later add fields without changing any
of the code that just want to change the eval time.
This also provides a fix for T75553, although it does require a change
to the custom driver function. The driver should call
`custom_function(depsgraph)`, and the function should use that depsgraph
instead of information from `bpy.context`.
Reviewed By: brecht, sergey
Differential Revision: https://developer.blender.org/D8047
All the driver-specific code in `fcurve.c` has been moved into a new file
`fcurve_driver.c`. The corresponding declarations have been moved from
`BKE_fcurve.h` to `BKE_fcurve_driver.h`.
All the `#include "BKE_fcurve.h"` statements have been investigated and
replaced with `BKE_fcurve_driver.h` where necessary.
No functional changes.
BF-admins agree to remove header information that isn't useful,
to reduce noise.
- BEGIN/END license blocks
Developers should add non license comments as separate comment blocks.
No need for separator text.
- Contributors
This is often invalid, outdated or misleading
especially when splitting files.
It's more useful to git-blame to find out who has developed the code.
See P901 for script to perform these edits.
