The main goal of these changes is to support checking if some data has
been changed over time. This is used by the WIP simulation nodes during
baking to detect which attributes have to be stored in every frame because
they have changed.
By using a combination of a weak user count and a version counter, it is
possible to detect that an attribute (or any data controlled by implicit
sharing) has not been changed with O(1) memory and time. It's still
possible that the data has been changed multiple times and is the same
in the end and beginning of course. That wouldn't be detected using this
mechanism.
The `ImplicitSharingInfo` struct has a new weak user count. A weak
reference is one that does not keep the referenced data alive, but makes sure
that the `ImplicitSharingInfo` itself is not deleted. If some piece of
data has one strong and multiple weak users, it is still mutable. If the
strong user count goes down to zero, the referenced data is freed.
Remaining weak users can check for this condition using `is_expired`.
This is a bit similar to `std::weak_ptr` but there is an important difference:
a weak user can not become a strong user while one can create a `shared_ptr`
from a `weak_ptr`. This restriction is necessary, because some code might
be changing the referenced data assuming that it is the only owner. If
another thread suddenly adds a new owner, the data would be shared again
and the first thread would not have been allowed to modify the data in
the first place.
There is also a new integer version counter in `ImplicitSharingInfo`.
It is incremented whenever some code wants to modify the referenced data.
Obviously, this can only be done when the data is not shared because then
it would be immutable. By comparing an old and new version number of the
same sharing info, one can check if the data has been modified. One has
to keep a weak reference to the sharing info together with the old version
number to ensure that the new sharing info is still the same as the old one.
Without this, it can happen that the sharing info was freed and a new
one was allocated at the same pointer address. Using a strong reference
for this purpose does not work, because then the data would never be
modified because it's shared.
Implicit sharing means attribute ownership is shared between geometry
data-blocks, and the sharing happens automatically. So it's unnecessary
to choose whether to enable it when copying a mesh.
For example
```
OIIOOutputDriver::~OIIOOutputDriver()
{
}
```
becomes
```
OIIOOutputDriver::~OIIOOutputDriver() {}
```
Saves quite some vertical space, which is especially handy for
constructors.
Pull Request: https://projects.blender.org/blender/blender/pulls/105594
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
- Added space below non doc-string comments to make it clear
these aren't comments for the symbols directly below them.
- Use doxy sections for some headers.
- Minor improvements to doc-strings.
Ref T92709
Previously, the spreadsheet editor could only show data of the original
and of the final evaluated object. Now it is possible to show the data
at some intermediate stages too.
For that the mode has to be set to "Node" in the spreadsheet editor.
Furthermore, the preview of a specific node has to be activated by
clicking the new icon in the header of geometry nodes.
The exact ui of this feature might be refined in upcoming commits.
It is already very useful for debugging node groups in it's current
state though.
Differential Revision: https://developer.blender.org/D10875
Currently the implementations specific to each geometry type are in
the same file. This makes it difficult to tell which code is generic
for all component types and which is specific to a certain type.
The two files, `attribute_access.cc`, and `geometry_set.cc` are
also getting quite long.
This commit splits up the implementation for every geometry component,
and adds an internal header file for the common parts of the attribute
access code. This was discussed with Jacques Lucke.
