This is the first builtin array attribute, with one of the objectives
being an ability to support an arbitrary count of per-vertex weights in
a single contiguous attribute without the complexity of having to go
through several four-component attributes.
On the shader side it still needs to get cut into at most four
components per attribute, but there's no reason for such limitation to
get propagated here as well.
Co-authored-by: Vladimír Vondruš <mosra@centrum.cz>
I'm not sure why this restriction was there as nothing was preventing
them from being used. The attribute is only accessible through the
typeless attribute(), which gives back
`Containers::StridedArrayView2D<const char>` with second dimension size
being set to the full stride. And there it doesn't matter if the format
is an array or not.
This will be useful for joint IDs and weights, for example doing crazy
things like packing the IDs into an array of 8 4-bit numbers, saving
half the memory compared to the smallest builtin representation using
UnsignedByte[8].
A lot of pain went into creating owned mesh data even though it was
completely unnecessary in retrospect. Originally I thought "let's not
use any advanced feature" but the verbosity is just not worth it.
In the recent-ish SceneData tests I went with non-owned data already,
and it was much simpler. It's a learning process even for using my own
APIs, huh.
I realized those are too annoying when writing a glTF exporter which
contains a lot of switches over enums. And as further shown by the diff,
those were only inflicting additional pain in *all* switch statements,
nothing else, no other added value. And everywhere else the helpers are
the designated way to deal with those, so there's no point in having an
explicit enum value denoting start of a "custom range".
It wasn't even any convenient to have it in the enum, as the extra
effort needed for casting actually made it *exactly* the same length as
if I'd just use a separately-defined constant.
Again not publicly documented because I don't like the naming and I
don't have the full behavior and interactions figured out yet -- i.e.,
an array of VertexFormats would be printed with Debug::packed as a long
string of characters without any whitespace. Not good, thus this
feature probably needs to be split in two, with this being named
"compact" or something else.
It's dangerous, as in case of failure it will attempt to print them as
strings. Plus now with latest de-std-string-ification of TestSuite it
causes the compilation to fail due to an ambigupus overload.
This should eventually be catched and disallowed directly by the Tester
class.
This mirrors what's done already for implementation-specific vertex
formats, thus:
* Ability to construct the classes without tripping up when trying to
check for type size in various asserts
* Providing a zero-size type-erased access in indices() and
mutableIndices()
* Disallowing typed and convenience access
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.
Because otherwise we don't properly test all cases. Case in point --
attributeData(UnsignedInt) wasn't correctly propagating the array size,
causing the new tests to fail. Fix in the next commit.
The array size is always last, defaulting to 0. This makes it consistent
with the offset-only constructor and removes two unnecessary overloads.
It's a breaking change, but I don't think array attributes have many
users yet -- and better to do this now than later. In any case, sorry
about breaking your code.
While 27f6cc309d made it easier to create
references to attribute-less meshes by avoiding a branch on
attributeCount() (and then using a constructor with explicit vertex
count), code still had to branch on isIndexed() because indices() could
be called only on indexed meshes. This change allows code like
Trade::MeshData reference{data.primitive(),
{}, data.indexData(), Trade::MeshIndexData{data.indices()},
{}, data.vertexData(), Trade::meshAttributeDataNonOwningArray(data.attributeData()),
data.vertexCount()};
which works correctly for all cases and doesn't introduce extra branches
and code paths that would need to be tested. While definitely better, I
might still give up at some point and introduce some
Trade::MeshData::nonOwningImmutableReference() helper for this.
Originally wanted to offload this to someone else, but then realized I
need those for generic vertex attribute definitions, which I need for
instancing, which I need now. So here it is, at the bottom of the
dependency chain.
Until now, except for an attribute-less index-less mesh, the vertex
count was only implicitly taken from passed attributes, but it was
severely limiting:
- There was no way to set vertex count for an attribute-less
indexed mesh, which didn't make sense
- All code that made non-owning MeshData instances referencing another
MeshData had to explicitly handle the attribute-less corner case to
avoid vertex count getting lost
- Offset-only attributes couldn't be used to specify static layout of
meshes with dynamic vertex count, causing unnecessary extra
allocations especially in the Primitives library.
Squareys