This is another blog post on OpenGL and Vulkan Interoperability. It’s not really a description of a new use case as the Piglit test I am going to describe is quite similar to the previous example we’ve seen where we reused a Vulkan pixel buffer from OpenGL. This Piglit test was written because there’s an interesting issue (Issue 7) in the spec according to which overwriting Vulkan buffers with glBufferSubData is not possible! This is interesting because we can overwrite textures but not buffers. When we attempt to overwrite a buffer using glBufferSubData the driver must return an Invalid Operation Error and this is what we tested with the vk-pix-buf-update-errors test that can be found in tests/spec/ext_external_objects directory like all other tests we’ve seen so far.
This is the 4th post on OpenGL and Vulkan Interoperability on Linux. The first one was an introduction to EXT_external_objects and EXT_external_objects_fd extensions, the second was describing a simple interoperability use case where a Vulkan allocated textured is filled by OpenGL, and the third was about a slightly more complex use case where a Vulkan texture was filled by Vulkan and displayed by OpenGL. In this 4th and last post about shared textures, we are going to see a use case where a Vulkan texture is filled by Vulkan, then gets overwritten by OpenGL, then is read back from Vulkan and then displayed again using OpenGL. This more complex use case has also been written for Piglit using the small Vulkan framework I’ve written to test the external objects extensions. The source code can be found inside the tests/spec/ext_external_objects directory of the mesa/piglit master branch.
We are going to see a slightly more complex case of Vulkan/GL interoperability where an image is allocated and filled using Vulkan and then it is displayed using OpenGL. This case is implemented in Piglit’svk-image-display test for a 2D RGBA texture (which is one of the most commonly used texture types).
Remember that the code for the test and the Vulkan helper/framework functions as well as the interoperability functions is in tests/spec/ext_external_objects/ Piglit directory.
We are going to see a very simple case of Vulkan/GL interoperability where an image is allocated using Vulkan and filled using OpenGL. This case is implemented in Piglit’s vk-image-overwrite test for images of different formats.
As there were no conformance tests (CTS) for this extension, and we needed to test it, we have written (and we are still writing) small tests for piglit that allow the exchange and the synchronization of the exchange of resources such as buffers, textures, and depth or stencil buffers.
The required Vulkan implementation version for a Vkrunnershader test can now be specified in its [require] section. Tests that are targeting Vulkan versions that aren’t supported by the device driver will be skipped.
The video mostly shows the behavior of some GL calls and operations with and without the patches that improve the emulation of the ETC/EAC formats on Gen7 GPUs. The same programs run first with the previous ETC/EAC emulation (upper terminal) and then with the new one (lower terminal).