| Zink |
| ==== |
| |
| Overview |
| -------- |
| |
| The Zink driver is a Gallium driver that emits Vulkan API calls instead |
| of targeting a specific GPU architecture. This can be used to get full |
| desktop OpenGL support on devices that only support Vulkan. |
| |
| Features |
| -------- |
| |
| The feature-level of Zink depends on two things; what's implemented in Zink, |
| as well as the features of the Vulkan driver. |
| |
| OpenGL 2.1 |
| ^^^^^^^^^^ |
| |
| OpenGL 2.1 is the minimum version Zink can support, and will always be |
| exposed, given Vulkan support. There's a few features that are required |
| for correct behavior, but not all of these are validated; instead you'll |
| see rendering-issues and likely validation error, or even crashes. |
| |
| Here's a list of those requirements: |
| |
| * Vulkan 1.0 |
| * ``VkPhysicalDeviceFeatures``: |
| |
| * ``logicOp`` |
| * ``fillModeNonSolid`` |
| * ``wideLines`` |
| * ``largePoints`` |
| * ``alphaToOne`` |
| * ``shaderClipDistance`` |
| |
| * Instance extensions: |
| |
| * `VK_KHR_get_physical_device_properties2`_ |
| * `VK_KHR_external_memory_capabilities`_ |
| |
| * Device extensions: |
| |
| * `VK_KHR_maintenance1`_ |
| * `VK_KHR_external_memory`_ |
| |
| OpenGL 3.0 |
| ^^^^^^^^^^ |
| |
| For OpenGL 3.0 support, the following additional device extensions are |
| required to be exposed and fully supported: |
| |
| * `VK_EXT_transform_feedback`_ |
| * `VK_EXT_conditional_rendering`_ |
| |
| |
| OpenGL 3.1 |
| ^^^^^^^^^^ |
| |
| For OpenGL 3.1 support, the following additional ``VkPhysicalDeviceLimits`` |
| are required: |
| |
| * ``maxPerStageDescriptorSamplers`` ≥ 16 |
| |
| OpenGL 3.2 |
| ^^^^^^^^^^ |
| |
| For OpenGL 3.2 support, the following additional ``VkPhysicalDeviceFeatures`` |
| are required to be supported, although some of these might not actually get |
| verified: |
| |
| * ``depthClamp`` |
| * ``geometryShader`` |
| * ``shaderTessellationAndGeometryPointSize`` |
| |
| OpenGL 3.3 |
| ^^^^^^^^^^ |
| |
| For OpenGL 3.3 support, the following additional ``VkPhysicalDeviceFeatures`` |
| are required to be supported, although some of these might not actually get |
| verified: |
| |
| * ``VkPhysicalDeviceFeatures`` |
| |
| * ``occlusionQueryPrecise`` |
| |
| * Device extensions: |
| |
| * `VK_EXT_vertex_attribute_divisor`_ |
| |
| Debugging |
| --------- |
| |
| There's a few tools that are useful for debugging Zink, like this environment |
| variable: |
| |
| .. envvar:: ZINK_DEBUG <flags> ("") |
| |
| ``nir`` |
| Print the NIR form of all shaders to stderr. |
| ``spirv`` |
| Write the binary SPIR-V form of all compiled shaders to a file in the |
| current directory, and print a message with the filename to stderr. |
| ``tgsi`` |
| Print the TGSI form of TGSI shaders to stderr. |
| |
| Vulkan Validation Layers |
| ^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| Another useful tool for debugging is the `Vulkan Validation Layers |
| <https://github.com/KhronosGroup/Vulkan-ValidationLayers/blob/master/README.md>`_. |
| |
| The validation layers effectively insert extra checking between Zink and the |
| Vulkan driver, pointing out incorrect usage of the Vulkan API. The layers can |
| be enabled by setting the environment variable :envvar:`VK_INSTANCE_LAYERS` to |
| "VK_LAYER_KHRONOS_validation". You can read more about the Validation Layers |
| in the link above. |
| |
| IRC |
| --- |
| |
| In order to make things a bit easier to follow, we have decided to create our |
| own IRC channel. If you're interested in contributing, or have any technical |
| questions, don't hesitate to visit `#zink on FreeNode |
| <irc://irc.freenode.net/zink>`_ and say hi! |
| |
| |
| .. _VK_KHR_get_physical_device_properties2: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_get_physical_device_properties2.html |
| .. _VK_KHR_external_memory_capabilities: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_external_memory_capabilities.html |
| .. _VK_KHR_maintenance1: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_maintenance1.html |
| .. _VK_KHR_external_memory: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_external_memory.html |
| .. _VK_EXT_transform_feedback: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_transform_feedback.html |
| .. _VK_EXT_conditional_rendering: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_conditional_rendering.html |
| .. _VK_EXT_vertex_attribute_divisor: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_vertex_attribute_divisor.html |