Basically mirroring the changes done for Corrade::Compare::*File*,
including storing the filenames as string views to avoid unnecessary
copies (and then paying extra attention to not pass temporaries to them
in its own tests).
Mainly to have feature parity with Flat and Phong -- otherwise switching
to draw a wireframe on an instanced mesh would be too annoying. Also, if
we have multidraw there already, why not instancing as well.
Also not something the classic GPU vertex pipeline can handle, but
useful for other scenarios. Subsequently a support for array indices
will be added, allowing to directly represent for example OBJ files,
where each attribute has its own index buffer.
This is not something the classic GPU vertex pipeline can handle
(except maybe Vulkan, which can handle zero strides for instanced
attributes?), but useful for other scenarios. This means existing code
needs to be aware of and handle the new corner case.
Same as with MeshData2D/3D, the original ObjectData API and plugin
interfaces are preserved to keep existing code as well as existing
importer implementations working. As Magnum's own importers will get
updated to the new SceneData workflow, a backward compatibility layer
provided that translates it to the subset that the legacy ObjectData
understands.
With this commit, both existing plugin code can build (and test against)
the new workflow, and any ports to the new workflow can test against the
legacy interfaces. Except that for now the compatibility layer doesn't
deal with objects that have more than one mesh or for example a light
and a camera attached, this will be done in a separate step.
Looking at the snippets, these seem to have been written back when there
was no builtin shaders yet, it seems, not to mention
MeshTools::compile(), Trade::MeshData or any of the other high-level
APIs. Rather overwhelming to just throw huge code snippets at the user,
explaining a workflow with a custom-made mesh that's going to be drawn
with a custom-made shader, which is like level 999 of using the GL
library.
It was rather discouraging to start "Basic usage" with a boring-ass long
snippet. On the other hand showing just compile() first would lead
people to think it's all some opaque magic, so trying to balance that a
bit.
Also why the hell was the compile() snippet showing the horrendous GL
way of specifying attribute formats? This is not great either but at
least not redundant.
Using openMemory() instead of openData() allows the implementation to
assume the data will stay in scope for as long as needed, which can
prevent unnecessary copies in some plugin implementations.
It warranted a new flag, DataFlag::ExternallyOwned, to describe this
kind of memory. I couldn't reuse Owned as that's used for allocations
owned by the instance, which is too little for certain future use cases.
For example returning *Data instances referencing an Owned memory would
mean the user has to assume the memory is gone when the importer
instance is gone, and that's generally not true for memory passed to
openMemory().
Originally I thought I would do this later, but then realized the
existing plugin implementations would need to get all updated again to
be aware of the new flag, with some being forgotten, and it's just
easier to do the whole thing in a single step.
This allows to better describe memory ownership and transfer it instead
of forcing the plugins to allocate their own local copy if the import
happens in-place on the imported data. Right now that's mainly for the
openFile() use case, which implicitly allocated an Array with file
contents only to pass it to openData() which then made a copy because it
could not make any assumption about data scope.
In other words, certain plugins (TgaImporter, KtxImporter, DdsImporter,
CgltfImporter and possibly others) will now have their peak memory usage
*halved*.
Hah, so many overloads. Not providing mutable access to keys or layer
offsets as that would break the invariant of the internal array always
being sorted.
And update docs in Matrix[34]::rotation() and related functions to note
this. This is a breaking change that may cause existing code to start
asserting.
Interestingly enough, there were no docs whatsoever for image and scene
conversion, and neither it was mentioned what all scene data can be
imported. Sigh.
Breaking this macro yet again, sorry -- now the result values are
specified last and there can be any number of them, however they need to
be all prefixed, as adding the prefix implicitly with the macro would be
too much of a pain to implement, especially given the poor preprocessor
capabilities of MSVC.
Together with DescriptorBindingFlags, because it affects the design in a
rather specific way and it wouldn't make sense to postpone this and
forget all again until it becomes needed.
Vladimír Vondruš