Remove `const` from pass-by-value parameters in function declarations.
The variables passed as parameters can never be modified by the function
anyway, so declaring them as `const` is meaningless. Having the
declaration there could confuse, especially as it suggests it does have
a meaning, training people to write meaningless code.
This will help detecting missing API changes. Those keywords were added
on classes which did not already use them. Also added missing
`accepts_object_type()` on NURBS reader.
Previously fluid simulation and Alembic modifiers had a dedicated function
to query the velocity for motion blur. Now use a more generic system where
those modifiers output a velocity attribute.
Advantages:
* Geometry and particle nodes can output velocity through the same mechanism,
or read the attribute coming from earlier modifiers.
* The velocity can be preserved through modifiers like subdivision surface or
auto smooth.
* USD and Alembic previously only output velocity from fluid simulation, now
they work with velocity from other sources too.
* Simplifies the code for renderers like Cycles and exporters like
Alembic and USD.
This breaks compatibility:
* External renderers and exporters accessing these velocities through the
Python API now need to use the attribute instead.
* Existing modifier node setups that create an attribute named "velocity"
will render differently with motion blur.
Differential Revision: https://developer.blender.org/D12305
This commit only moves code into the `blender::io::alembic` namespace,
it does not move `static` functions into an anonymous namespace.
No functional changes.
This moves the `alembic`, `avi`, `collada`, and `usd` modules into a common
`io` directory.
This also cleans up some `#include "../../{somedir}/{somefile}.h"` by
adding `../../io/{somedir}` to `CMakeLists.txt` and then just using
`#include "{somefile}.h"`.
No functional changes.
