Commit Graph

43 Commits

Author SHA1 Message Date
Jeroen Bakker
f9aca93a47 Vulkan: Add Support for sRGB Framebuffer Enablement
Allow binding of framebuffers without sRGB to linear transform.
`GPU_framebuffer_bind_no_srgb`. This Patch removes color transform
artifacts in node, image and sequence editor.

When the framebuffer is an srgb framebuffer and it is bound without
the transformation, the SRGB textures are bound as UNORM variants.

As framebuffer, render pass and subpass recreation is ensured by
`VKCommandBuffer` we don't need to mark the framebuffer dirty at
this time. Later on we can optimize this by adding a state changed
detection for framebuffers and render passes.

Pull Request: https://projects.blender.org/blender/blender/pulls/113838
2023-10-19 14:41:18 +02:00
Jeroen Bakker
ad93324580 Vulkan: Add support for Framebuffer Depth Blit
This PR adds support for `GPU_framebuffer_blit` When used with `GPU_DEPTH_BIT`.
The challenge with is that not all GPUs support using a depth texture as a blit destination.

An AMD GPU doesn't support a depth buffer with stencil buffer as blit destination.
![image](/attachments/130e7e38-2dbc-4653-950c-2234bd5bad52)
> NOTE: AMD GPUs don't support 24 bit unsigned normalized depth textures at all.

In all cases when we use depth blitting we are blitting the whole texture
and in stead we can use a texture copy.

A negative effect is that we need to unbind the framebuffer when copying
depth textures, but a positive effect is that we can use a data transfer function what should
theoretically be faster.

This should be revisited when we are investigating in areas to improve the
performance of the Vulkan backend.

Pull Request: https://projects.blender.org/blender/blender/pulls/112674
2023-09-28 10:00:24 +02:00
Jeroen Bakker
e5a33b3b2c Vulkan: Rework Initializing/Allocating Textures
When initialy adding textures it wasn't possible to allocate during
initialization as its usage wasn't known. Bot Metal and Vulkan would do
a delayed allocation adding more checks when using textures.

Recently the behavior of setting texture usage was changed and now is
known when initializing textures. This PR makes advantage of this to
give correct feedback to the calling code if the texture can be created
and remove all the delayed allocating of textures.

Pull Request: https://projects.blender.org/blender/blender/pulls/112997
2023-09-28 09:38:52 +02:00
Jeroen Bakker
f7ccec2bcc Vulkan: Fix Generate Mipmaps for Array Textures
Array textures stores the array length inside the size of the image. In
vulkan the size mustn't contain the array length, but it should be set
as a separate parameter. This logic wasn't implemented when updating
the mipmap chain.

Patch also includes some smaller fixes where textures would not yet be
allocated on the device, but was expected to be.

Pull Request: https://projects.blender.org/blender/blender/pulls/112518
2023-09-18 13:45:53 +02:00
Jeroen Bakker
1daecc24d0 Vulkan: Postpone Resource Destruction
Resources can still be in use inside the vulkan command queue, when
they are destroyed. Especially as Vulkan doesn't allow resetting
bindings to nothing.

This PR will collect the resources that needs to be destroyed inside
the VKDevice and actually destroy the resources when on frame end.

The resources currently include:
* VkBuffer
* VkImage
* VkImageView
* VkFramebuffer
* VkRenderPass

Pull Request: https://projects.blender.org/blender/blender/pulls/112514
2023-09-18 13:42:17 +02:00
Jeroen Bakker
6920c690f1 Vulkan: Implement Component Swizzling
Component swizzling is part of an image view and localized in the code.
With component swizzling a different channel (or 0 or 1) can be read
when the component is accessed.

Pull Request: https://projects.blender.org/blender/blender/pulls/112273
2023-09-12 11:54:57 +02:00
Jeroen Bakker
ded7d96ba1 Vulkan: Texture View
Adding support for Texture View in Vulkan backend.

When a VKTexture is a texture view many options become
irrelevant, but isn't actually clear via its API. Added
asserts to make sure that the usage is supported.

This patch allows rendering simple workbench-next scenes
without any validation errors.

Pull Request: https://projects.blender.org/blender/blender/pulls/110887
2023-09-12 11:18:38 +02:00
Jeroen Bakker
bee3f645d8 Vulkan: Rewrite GHOST_ContextVK
This is a rewrite of GHOST_ContextVK to align with Metal backend as described
in #111389 - solution 3 with the adaptation that GHOST is still responsible
for presenting the swap chain image and a post callback is still needed in
case the swapchain is recreated.

This PR also includes some smaller improvements in stability.

Technical documentation: https://developer.blender.org/docs/eevee_and_viewport/gpu/vulkan/swap_chain/

* Renderpasses and framebuffers are not owned anymore by GHOST_ContextVK
* VKFramebuffer doesn't contain a swap chain image.
* Swapchain images can only be used as a blit destination or present source.
  Not as an attachment.
* GHOST_ContextVK::swapBuffers would call a callback with the image the
  GPU module needs to blit the results to.
* Clearing of depth/stencil attachments when no depth write state is set.
* Enable VK_KHR_maintenance4 to relax the stage interface mapping.
* Removes most vulkan validation warnings/errors.
* Detection of frame buffer changes that needs to be applied before
  performing a command requiring render pass (draw/clear attachment)

**Benefits**

* Late retrieval of a swap chain image results in better overall performance as
  Blender doesn't need to wait until the image is presented on the screen.
* Easier API and clearer state (transitions)
* More control over Image layouts and command buffer states. (Better alignment with
  Vulkan API)

Pull Request: https://projects.blender.org/blender/blender/pulls/111473
2023-08-29 15:05:08 +02:00
Jeroen Bakker
2af2a11651 Vulkan: Use Correct Image Aspects
Depending on the usage of an image/image view different image aspect
requirements need to be used. When changing the layout of an image
all aspects needs to be included. When using it as a sampler or
framebuffer attachment only one aspect can be used.

This change also remove duplicated code when creating image views.

Pull Request: https://projects.blender.org/blender/blender/pulls/111349
2023-08-22 11:00:43 +02:00
Campbell Barton
e955c94ed3 License Headers: Set copyright to "Blender Authors", add AUTHORS
Listing the "Blender Foundation" as copyright holder implied the Blender
Foundation holds copyright to files which may include work from many
developers.

While keeping copyright on headers makes sense for isolated libraries,
Blender's own code may be refactored or moved between files in a way
that makes the per file copyright holders less meaningful.

Copyright references to the "Blender Foundation" have been replaced with
"Blender Authors", with the exception of `./extern/` since these this
contains libraries which are more isolated, any changed to license
headers there can be handled on a case-by-case basis.

Some directories in `./intern/` have also been excluded:

- `./intern/cycles/` it's own `AUTHORS` file is planned.
- `./intern/opensubdiv/`.

An "AUTHORS" file has been added, using the chromium projects authors
file as a template.

Design task: #110784

Ref !110783.
2023-08-16 00:20:26 +10:00
Jeroen Bakker
d84a64900f Vulkan: Device Context Resource Management
The current Vulkan resource management has some issues as context that
are not active can still use resources that are freed via another
context.

When this happens incorrect data can be read on the GPU and even crash
Blender. When trying to bind something that now contains other memory
pointers.

This change introduces that contexts are tracked via the device.
Context will be registered/unregistered with the device instance.
Unbinding of resources must pass the device and the device will check
all registered contexts. Binding of resources will happen via the active
context only.

On user perspective this now allowes:
- Opening/switching files
- Switching workspaces
- Switching render engines

Pull Request: https://projects.blender.org/blender/blender/pulls/108968
2023-06-15 08:14:37 +02:00
Campbell Barton
d4b23cae8f Cleanup: use C-style comments for descriptive text 2023-06-14 12:20:06 +10:00
Jeroen Bakker
2ee2ae93fb Vulkan: Initial Cube(Array) Support
This PR adds initial cube (array) support. Depending on how the texture
is used a different image view is created. When used as a framebuffer
attachment only a single side of the cubemap is attached. The image
view is attached as a 2d texture array. When used as a shader resource
the image view is a cubemap.

Also adds test cases to test both scenarios.

Pull Request: https://projects.blender.org/blender/blender/pulls/108794
2023-06-09 16:09:54 +02:00
Campbell Barton
2f1899a7fa Cleanup: spelling in comments 2023-06-09 11:40:50 +10:00
Jeroen Bakker
513250051e Vulkan: Image Views
The ownership of image views depends on how they are used. When used as
an framebuffer attachment the image view is owned by the framebuffer.
When used as a image/texture in a shader the ownership of the image view
is the texture itself.

Pull Request: https://projects.blender.org/blender/blender/pulls/108765
2023-06-08 16:07:38 +02:00
Jeroen Bakker
c71d198dfd Vulkan: Mipmap Generation
Implement Mipmap generation for the Vulkan backend.
This patch implements `GPU_texture_update_mipmap_chain`.

Pull Request: https://projects.blender.org/blender/blender/pulls/108699
2023-06-08 09:15:07 +02:00
Jeroen Bakker
2231b819a5 Vulkan: Workaround for 24bit depth component
Some vulkan platforms don't support 24bit depth components. In this
case we will allocate float depth component. During readback the data
should be converted back to what is expected.

Pull Request: https://projects.blender.org/blender/blender/pulls/108698
2023-06-08 08:53:12 +02:00
Sergey Sharybin
c1bc70b711 Cleanup: Add a copyright notice to files and use SPDX format
A lot of files were missing copyright field in the header and
the Blender Foundation contributed to them in a sense of bug
fixing and general maintenance.

This change makes it explicit that those files are at least
partially copyrighted by the Blender Foundation.

Note that this does not make it so the Blender Foundation is
the only holder of the copyright in those files, and developers
who do not have a signed contract with the foundation still
hold the copyright as well.

Another aspect of this change is using SPDX format for the
header. We already used it for the license specification,
and now we state it for the copyright as well, following the
FAQ:

    https://reuse.software/faq/
2023-05-31 16:19:06 +02:00
Jeroen Bakker
004ce8fc4e Vulkan: Add Support For Texture Buffers
Texture buffers are vbos that can be sampled as textures inside shaders.
This adds support for them to the Vulkan Backend.

Pull Request: https://projects.blender.org/blender/blender/pulls/108193
2023-05-30 13:54:51 +02:00
Jeroen Bakker
3f89ec2866 Vulkan: Copy Between Textures
This PR adds support for copying between two textures.

Pull Request: https://projects.blender.org/blender/blender/pulls/108413
2023-05-30 13:50:35 +02:00
Jeroen Bakker
a08652b56c Vulkan: Area Readback of Framebuffer Textures
This PR adds the ability to only read back an area of a framebuffer
texture. It also adds the ability to read back from the depth
attachment.

Also reduces the amount of needed memory and reduces the CPU cycles
by reading back directly into the memory provided by the user. The
previous implementation wasn't able to do so as the `VKTexture::read`
function always returned a new buffer. The introduced
`VKTexture::read_sub` works on a pre-allocated buffer.

Pull Request: https://projects.blender.org/blender/blender/pulls/108418
2023-05-30 13:47:55 +02:00
Jason Fielder
ae405639e7 Metal: Stencil texture view support
Adds stencil texture view support for Metal, allowing reading of
stencil component during texture sample/read.

Stencil view creation refactored to use additional parameter in
textureview creation function, due to deferred stencil parameter
causing double texture view creation in Metal, when this should
ideally be provided upfront.

Authored by Apple: Michael Parkin-White

Pull Request: https://projects.blender.org/blender/blender/pulls/107971
2023-05-22 20:40:38 +02:00
Jeroen Bakker
809a5aa418 Vulkan: Initial Graphics Pipeline
Initial graphic pipeline targeting. The goal of this PR is to have an initial
graphics pipeline with missing features. It should help identifying
areas that requires engineering.

Current state is that developers of the GPU module can help with the many
smaller pieces that needs to be engineered in order to get it working. It is not
intended for users or developers from other modules, but your welcome to learn
and give feedback on the code and engineering part.

We do expect that large parts of the code still needs to be re-engineered into
a more future-proof implementation.

**Some highlights**:
- In Vulkan the state is kept in the pipeline. Therefore the state is tracked
  per pipeline. In the near future this could be used as a cache. More research
  is needed against the default pipeline cache that vulkan already provides.
- This PR is based on the work that Kazashi Yoshioka already did. And include
  work from him in the next areas
  - Vertex attributes
  - Vertex data conversions
  - Pipeline state
- Immediate support working.
- This PR modifies the VKCommandBuffer to keep track of the framebuffer and its
  binding state(render pass). Some Vulkan commands require no render pass to be
  active, other require a render pass. As the order of our commands on API level
  can not be separated this PR introduces a state engine to keep track of the
  current state and desired state. This is a temporary solution, the final
  solution will be proposed when we have a pixel on the screen. At that time
  I expect that we can design a command encoder that supports all the cases
  we need.

**Notices**:
- This branch works on NVIDIA GPUs and has been validated on a Linux system. AMD
  is known not to work (stalls) and Intel GPUs have not been tested at all. Windows might work
  but hasn't been validated yet.
- The graphics pipeline is implemented with pixels in mind, not with performance. Currently
  when a draw call is scheduled it is flushed and waited until it is finished drawing, before
  other draw calls can be scheduled. We expected the performance to be worse that it actually
  is, but we expect huge performance gains in the future.
- Any advanced drawing (that is used by the image editor, compositor or 3d viewport) isn't
  implemented and might crash when used.
- Using multiple windows or resizing of window isn't supported and will stall the system.

Pull Request: https://projects.blender.org/blender/blender/pulls/106224
2023-05-11 13:01:56 +02:00
Jeroen Bakker
a0ea40034b Vulkan: Make ShaderInput Optional
ShaderInput lookup used to be explicit as in we know for sure that the
shader input exists. This was guarded by a assert. During development
of the graphics pipeline we came to the conclusion that this isn't
always the case due to its late bindings of resources.

This PR Makes the shader input lookup return an optional result.
This result can then be checked depending on the area where it is used
to validate the existence.

Pull Request: https://projects.blender.org/blender/blender/pulls/107735
2023-05-11 08:44:57 +02:00
Jeroen Bakker
63cc5a1e61 Vulkan: Frame Buffer Flipping
Vulkan coordinate system is flipped compared to OpenGL. This PR
flips the drawing when drawn to the on-screen frame buffer.
Offscreen frame buffers are still drawn upside down.

The flipping is done by making the viewport of the framebuffer negative.

Pull Request: https://projects.blender.org/blender/blender/pulls/107743
2023-05-09 09:22:26 +02:00
Jeroen Bakker
b0c7e83805 Cleanup: formatting
In recent changes to vulkan.
2023-05-04 10:23:15 +02:00
Jeroen Bakker
f428fd8229 Vulkan: Share Device Between Contexts
Previous GHOST_ContextVK would create a logical device for each
context. Blender uses multiple contexts at the same time and wasn't able
to share resources between them as the logical device where different.

This patch will create a single logical device and share them between
multiple contexts. This allows sharing memory/shaders between contexts
and make sure that all memory allocations are freed from the device it
was allocated from.

Some allocations in Blender are freed when there isn't a context, this
was failing in the previous implementation. We didn't noticed it before
as we didn't test multiple contexts.

This patch also moves device specific data structures from VKContext to
VKDevice like the descriptor pools, debug layers etc.

Pull Request: https://projects.blender.org/blender/blender/pulls/107606
2023-05-04 10:06:48 +02:00
Jason Fielder
36e1ebc78d Metal: Resolve runtime issues with texture views
When creating a texture view, Metal may require that the original
GPUTexture state is modified in some way. This may be a result
of deferred creation, or, to cache the texture view against the
source.

As a result, GPUTexture passed into GPU_texture_create_view
cannot be const.

Small fixes have also been made in the Metal texture
implementation to ensure correct function of texture views.

Authored by Apple: Michael Parkin-White

Pull Request: https://projects.blender.org/blender/blender/pulls/107167
2023-05-01 09:14:00 +02:00
Jeroen Bakker
89afdd6f24 Vulkan: Texture Unpacking
This PR adds support for `GPU_unpack_row_length_set` to the vulkan
backend.

Texture unpacking is used when uploading a part of a texture from
host memory to device memory.

Pull Request: https://projects.blender.org/blender/blender/pulls/107360
2023-04-26 09:23:58 +02:00
Campbell Barton
440cccecdc Cleanup: spelling in comments 2023-04-05 14:39:51 +10:00
Sergey Sharybin
a12a8a71bb Remove "All Rights Reserved" from Blender Foundation copyright code
The goal is to solve confusion of the "All rights reserved" for licensing
code under an open-source license.

The phrase "All rights reserved" comes from a historical convention that
required this phrase for the copyright protection to apply. This convention
is no longer relevant.

However, even though the phrase has no meaning in establishing the copyright
it has not lost meaning in terms of licensing.

This change makes it so code under the Blender Foundation copyright does
not use "all rights reserved". This is also how the GPL license itself
states how to apply it to the source code:

    <one line to give the program's name and a brief idea of what it does.>
    Copyright (C) <year>  <name of author>

    This program is free software ...

This change does not change copyright notice in cases when the copyright
is dual (BF and an author), or just an author of the code. It also does
mot change copyright which is inherited from NaN Holding BV as it needs
some further investigation about what is the proper way to handle it.
2023-03-30 10:51:59 +02:00
Sergey Sharybin
d32d787f5f Clang-Format: Allow empty functions to be single-line
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
2023-03-29 16:50:54 +02:00
Jeroen Bakker
aa69ec7f80 Vulkan: Clearing Framebuffer + Scissors
This PR adds support for clearing framebuffers and scissor testing.
Tweaks had to be made to VKTexture to keep track of its layout
on the device. Based on the actual call the layout can switch
to a more optimum layout.

For example during upload of a texture the texture will be converted
to a transfer destination optimized layout. When reading from the
texture it will be converted to a transfer source optimized layout.

The order of the attachments in the framebuffer follows the next rules

- When only color attachments are there the color attachments will
  be placed in the slot they are defined. This way it will match
  the ShaderCreateInfo binding location.
- When a stencil/depth attachment is added it will be placed
  right after the color attachments. When there isn't a color
  attachment it will be the first attachment.

Pull Request: https://projects.blender.org/blender/blender/pulls/106044
2023-03-28 11:51:32 +02:00
Jeroen Bakker
f8e190aac5 Cleanup: Silence Compilation Warnings
In recent Vulkan changes.

Pull Request: https://projects.blender.org/blender/blender/pulls/106204
2023-03-28 08:53:56 +02:00
Jeroen Bakker
08a6361b3f Vulkan: Texture Data Conversions
This PR adds basic support for texture update, read back and clearing
for Vulkan. In Vulkan we need to convert each data type ourselves as
vulkan buffers are untyped. Therefore this change mostly is about data
conversions.

Considerations:
- Use a compute shader to do the conversions:
  - Leads to performance regression as compute pipeline can stall
    graphics pipeline
  - Lead to additional memory usage as two staging buffers are needed
    one to hold the CPU data, and one to hold the converted data.
- Do inline conversion when sending the data to Vulkan using `eGPUDataFormat`
  - Additional CPU cycles required and not easy to optimize as it the
    implementation requires many branches.
- Do inline conversion when sending the data to Vulkan (optimized for CPU)

For this solution it was chosen to implement the 3rd option as it is fast
and doesn't require additional memory what the other options do.

**Use Imath/half.h**
This patch uses `Imath/half.h` (dependency of OpenEXR) similar to
alembic. But this makes vulkan dependent of the availability of
OpenEXR. For now this isn't checked, but when we are closer to
a working Vulkan backend we have to make a decision how to cope with
this dependency.

**Missing Features**

*Framebuffer textures*
This doesn't include all possible data transformations. Some of those
transformation can only be tested after the VKFramebuffer has been
implemented. Some texture types are only available when created for a
framebuffer. These include the depth and stencil variations.

*Component format*
Is more relevant when implementing VKVertexBuffer.

*SRGB textures*
SRGB encoded textures aren't natively supported on all platforms, in
all usages and might require workarounds. This should be done in a
separate PR in a later stage when we are required to use SRGB textures.

**Test cases**
The added test cases gives an overview of the missing bits and pieces of
the patch. When the implementation/direction is accepted more test cases
can be enabled/implemented.

Some of these test cases will skip depending on the actual support of
platform the tests are running on. For example OpenGL/NVidia will skip
the next test as it doesn't support the texture format on OpenGL, although
it does support it on Vulkan.

```
[ RUN      ] GPUOpenGLTest.texture_roundtrip__GPU_DATA_2_10_10_10_REV__GPU_RGB10_A2UI
[  SKIPPED ] GPUOpenGLTest.texture_roundtrip__GPU_DATA_2_10_10_10_REV__GPU_RGB10_A2UI [ RUN      ] GPUVulkanTest.texture_roundtrip__GPU_DATA_2_10_10_10_REV__GPU_RGB10_A2UI
[       OK ] GPUVulkanTest.texture_roundtrip__GPU_DATA_2_10_10_10_REV__GPU_RGB10_A2UI
```

Pull Request: https://projects.blender.org/blender/blender/pulls/105762
2023-03-24 08:09:19 +01:00
Jeroen Bakker
0ad06cd39d Vulkan: Automap Buffers.
It is recommended to map buffers once and not each time the
mapped memory is needed. This patch will map the buffer when
created and unmap the buffer when the buffer is freed.

This patch will reduce the overhead where the Vulkan driver or
the virtual memory manager needs to be accessed.

Pull Request: https://projects.blender.org/blender/blender/pulls/105588
2023-03-09 09:27:42 +01:00
Jeroen Bakker
8aedc03aa2 Vulkan: Calculate Correct Host and Device Memory Size.
Due to an error in GPU module we fixed the memory size in the
Vulkan backend. Last week the error has been fixed in the GPU module
so we can remove the temp fixes in the Vulkan backend.

Pull Request #105244
2023-02-27 12:56:05 +01:00
Campbell Barton
efb86b75ee Cleanup: comment block formatting 2023-02-27 21:51:57 +11:00
Jeroen Bakker
8c03410ebd Vulkan: Refactor shader interface.
Descriptor set locations are now determined in the
VKShaderInterface. Issues with the previous solution:

- Due to legacy code in GPU module the locations/bindings
  must be the same. Using one for something else might
  result in undesired lookups, incorrect resource
  bindings.
- Images/Textures reuses the same namespace, that didn't
  work as expected when looking up the resources via
  its binding.

This refactoring is required for adding support for
push constants.

Pull Request #105073
2023-02-22 14:42:01 +01:00
Jeroen Bakker
7fb1f060ff Vulkan: Initial Compute Shaders support
This patch adds initial support for compute shaders to
the vulkan backend. As the development is oriented to the test-
cases we have the implementation is limited to what is used there.

It has been validated that with this patch that the following test
cases are running as expected
- `GPUVulkanTest.gpu_shader_compute_vbo`
- `GPUVulkanTest.gpu_shader_compute_ibo`
- `GPUVulkanTest.gpu_shader_compute_ssbo`
- `GPUVulkanTest.gpu_storage_buffer_create_update_read`
- `GPUVulkanTest.gpu_shader_compute_2d`

This patch includes:
- Allocating VkBuffer on device.
- Uploading data from CPU to VkBuffer.
- Binding VkBuffer as SSBO to a compute shader.
- Execute compute shader and altering VkBuffer.
- Download the VkBuffer to CPU ram.
- Validate that it worked.
- Use device only vertex buffer as SSBO
- Use device only index buffer as SSBO
- Use device only image buffers

GHOST API has been changed as the original design was created before
we even had support for compute shaders in blender. The function
`GHOST_getVulkanBackbuffer` has been separated to retrieve the command
buffer without a backbuffer (`GHOST_getVulkanCommandBuffer`). In order
to do correct command buffer processing we needed access to the queue
owned by GHOST. This is returned as part of the `GHOST_getVulkanHandles`
function.

Open topics (not considered part of this patch)
- Memory barriers & command buffer encoding
- Indirect compute dispatching
- Rest of the test cases
- Data conversions when requested data format is different than on device.
- GPUVulkanTest.gpu_shader_compute_1d is supported on AMD devices.
  NVIDIA doesn't seem to support 1d textures.

Pull-request: #104518
2023-02-21 15:04:52 +01:00
Campbell Barton
79c82fc1c5 Cleanup: trailing space 2023-01-31 15:49:04 +11:00
Jeroen Bakker
09ee781a67 GPU: Add placeholders for PixelBuffer to vulkan backend.
PixelBuffer was recently introduced. This change adds empty placeholders to the
vulkan backend and other related API tweaks.
2022-12-02 08:35:17 +01:00
Jeroen Bakker
0e6f2d9fe0 GPU: Add placeholder for Vulkan backend.
This patch adds a placeholder for the vulkan backend.
When activated (`WITH_VULKAN_BACKEND=On` and `--gpu-backend vulkan`)
it might open a blender screen, but nothing should be visible as
none of the functions are implemented or otherwise crash on a nullptr.

This is expected as this is just a placeholder. The goal is to add shader compilation
+validation to this backend as one of the next steps so we can validate
changes to existing shaders on OpenGL, Metal and Vulkan at the same time.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D16338
2022-10-31 16:01:15 +01:00