This allows clients to initialize 3D image objects with data in a BC1,
BC2, or BC3 (aka DXTn, aka S3TC) format. Since Metal doesn't support
this natively, DXTn-compressed image data are manually decompressed
prior to upload or copying. This particular algorithm was derived from
Wine, from code originally authored by Connor McAdams. It's somewhat
primitive, and could probably stand some vectorization, but it's a good
first start.
The meat of the algorithm is pulled into a header, "MVKDXTnCodec.def",
intended to be used by both CPU and shader code. CPU uploads, which in
MoltenVK happen when binding a `VkDeviceMemory` object to an image, run
the code normally. GPU uploads, i.e. copying from a buffer to a texture,
run the algorithm as a compute shader, possibly storing the results to
an intermediate buffer to then copy directly to the texture.
Intermediate buffers are used when uploading to mip levels higher than
0, since desktop Metal doesn't support directly writing to higher mip
levels from a shader.
Only uploads are supported. Downloads are not implemented yet.
Theoretically, this could be extended to other compressed formats as
well, allowing MoltenVK to support all texture compression formats on
all platforms.
Decrease minimum swapchain images to 2.
Add MVKPhysicalDeviceMetalFeatures::minSwapchainImageCount & maxSwapchainImageCount.
Minor refactoring of mvkClamp() & MVKPhysicalDevice::getSurfacePresentModes().
Update VK_MVK_MOLTENVK_SPEC_VERSION to 15.
Update MoltenVK version to 1.0.30.
The fetchDependencies script puts build files in External/build directory.
Xcode puts build files in standard Library/.../DerivedData directory.
Copy compiled external static library files to External/build/iOS &
External/build/macOS regardless of location of intermediates.
Add separate ExternalDependencies Xcode project.
Move external dependencies to ExternalDependencies project.
The fetchDependencies script builds external dependencies libraries into External/build.
The fetchDependencies script prepares SPIRV-Tools without preparing glslang.
MoltenVK links to pre-built external dependency static libraries.
MoltenVK includes external library headers using full relative paths.
Instead of assuming that `kMVKFormatNone` means the format is
compressed. This makes the code doing these checks more obvious and
self-documenting.
Since I changed the public MoltenVK-specific API, I also bumped the
`VK_MVK_moltenvk` spec revision.
Since a pipeline might be shared between multiple draws, but those draws
could use different textures, it isn't tenable to have a single aux
buffer shared between those draws. Instead, we'll set up constant
buffers using the `setXxxBytes()` method on the command encoder. That
way, separate draws using the same pipeline won't interfere with each
other.
This change also uses separate buffers for the vertex and fragment
shaders, since they may have different sets of textures.
