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`` * Device extensions: * `VK_KHR_maintenance1`_ * `VK_EXT_custom_border_color` In addition to this, `VK_KHR_external_memory`_ is required to support the DRI code-path. We also require either the `VK_EXT_scalar_block_layout`_ extension or Vulkan 1.2, with the ``scalarBlockLayout`` feature. OpenGL 3.0 ^^^^^^^^^^ For OpenGL 3.0 support, the following additional requirements needs to be supported: * ``VkPhysicalDeviceFeatures``: * ``independentBlend`` * Device extensions: * `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 requirements needs to be supported, although some of these might not actually get verified: * ``VkPhysicalDeviceFeatures``: * ``occlusionQueryPrecise`` * Device extensions: * `VK_EXT_vertex_attribute_divisor`_ OpenGL 4.0 ^^^^^^^^^^ For OpenGL 4.0 support, the following additional requirements needs to be supported: * ``VkPhysicalDeviceFeatures``: * ``sampleRateShading`` * ``tessellationShader`` * ``imageCubeArray`` * Device extensions: * `VK_KHR_maintenance2`_ * Formats requiring ``VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT``: * ``VK_FORMAT_R32G32B32_SFLOAT`` * ``VK_FORMAT_R32G32B32_SINT`` * ``VK_FORMAT_R32G32B32_UINT`` OpenGL 4.1 ^^^^^^^^^^ For OpenGL 4.1 support, the following additional ``VkPhysicalDeviceLimits`` are required: * `maxImageDimension2D` ≥ 16384 * `maxViewports` ≥ 16 OpenGL 4.2 ^^^^^^^^^^ For OpenGL 4.2 support, the following additional requirements needs to be supported: * For Vulkan 1.2 and above: * ``VkPhysicalDeviceVulkan11Features``: * ``shaderDrawParameters`` * ``vertexPipelineStoresAndAtomics`` * ``fragmentStoresAndAtomics`` * ``textureCompressionBC`` * For Vulkan 1.1 and below: * Device extensions: * `VK_KHR_shader_draw_parameters`_ * Formats requiring ``VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT``: * ``VK_FORMAT_BC7_UNORM_BLOCK`` * ``VK_FORMAT_BC7_SRGB_BLOCK`` * ``VK_FORMAT_BC6H_SFLOAT_BLOCK`` * ``VK_FORMAT_BC6H_UFLOAT_BLOCK`` OpenGL 4.3 ^^^^^^^^^^ For OpenGL 4.3 support, the following additional requirements needs to be supported: * ``VkPhysicalDeviceFeatures``: * ``robustBufferAccess`` * ``multiViewport`` * Formats requiring ``VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT``: * ``VK_FORMAT_R8G8B8A8_UNORM`` * ``VK_FORMAT_R8G8B8A8_SRGB`` * ``VK_FORMAT_R16_UNORM`` * ``VK_FORMAT_R16G16_UNORM`` * ``VK_FORMAT_R16_SNORM`` * ``VK_FORMAT_R16G16_SNORM`` * ``VK_FORMAT_D32_SFLOAT_S8_UINT`` OpenGL 4.4 ^^^^^^^^^^ For OpenGL 4.4 support, the following additional requirements needs to be supported: * Formats requiring ``VK_FORMAT_FEATURE_VERTEX_BUFFER_BIT``: * ``VK_FORMAT_B10G11R11_UFLOAT_PACK32`` * Device extensions: * `VK_KHR_sampler_mirror_clamp_to_edge`_ OpenGL 4.5 ^^^^^^^^^^ For OpenGL 4.5 support, the following additional ``VkPhysicalDeviceFeatures`` are required to be supported * ``shaderCullDistance`` OpenGL 4.6 ^^^^^^^^^^ For OpenGL 4.6 support, the following additional ``VkPhysicalDeviceFeatures`` are required to be supported * ``VkPhysicalDeviceFeatures``: * ``samplerAnisotropy`` * ``pipelineStatisticsQuery`` * ``depthBiasClamp`` * Device extensions: * `VK_KHR_draw_indirect_count`_ Debugging --------- There's a few tools that are useful for debugging Zink, like this environment variable: .. envvar:: ZINK_DEBUG ("") ``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. ``validation`` Dump Validation layer output. Vulkan Validation Layers ^^^^^^^^^^^^^^^^^^^^^^^^ Another useful tool for debugging is the `Vulkan Validation Layers `_. 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 `_ and say hi! .. _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_scalar_block_layout: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_scalar_block_layout.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 .. _VK_KHR_maintenance2: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_maintenance2.html .. _VK_KHR_shader_draw_parameters: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_shader_draw_parameters.html .. _VK_KHR_draw_indirect_count: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_draw_indirect_count.html .. _VK_KHR_sampler_mirror_clamp_to_edge: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_sampler_mirror_clamp_to_edge.html