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Querying Properties, Extensions, Features, Limits, and Formats

One of Vulkan's main features is that is can be used to develop on multiple platforms and devices. To make this possible, an application is responsible for querying the information from each physical device and then basing decisions on this information.

The items that can be queried from a physical device

  • Properties
  • Features
  • Extensions
  • Limits
  • Formats

Properties

There are many other components in Vulkan that are labeled as properties. The term "properties" is an umbrella term for any read-only data that can be queried.

Extensions

Check out the Enabling Extensions chapter for more information.

There is a Registry with all available extensions.

There are many times when a set of new functionality is desired in Vulkan that doesn't currently exist. Extensions have the ability to add new functionality. Extensions may define new Vulkan functions, enums, structs, or feature bits. While all of these extended items are found by default in the Vulkan Headers, it is undefined behavior to use extended Vulkan if the extensions are not enabled.

Features

Checkout the Enabling Features chapter for more information.

Features describe functionality which is not supported on all implementations. Features can be queried and then enabled when creating the VkDevice. Besides the list of all features, some features are mandatory due to newer Vulkan versions or use of extensions.

A common technique is for an extension to expose a new struct that can be passed through pNext that adds more features to be queried.

Limits

Limits are implementation-dependent minimums, maximums, and other device characteristics that an application may need to be aware of. Besides the list of all limits, some limits also have minimum/maximum required values guaranteed from a Vulkan implementation.

Formats

Every VkBuffer and VkImage requires a format from the supported Vulkan VkFormat list. The supported formats may vary across implementations, but a minimum set of format features are guaranteed. An application can query for the supported format properties.

Each format has a set of VkFormatFeatureFlagBits for how the format is supported or not. These features bits are grouped further for how the format is used.

Example: One can check if the VK_FORMAT_R8_UNORM format supports being sampled when an images is created with a tiling parameter of VK_IMAGE_TILING_LINEAR.

To do this, query the linearTilingFeatures flags for VK_FORMAT_R8_UNORM to see if the VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT is set for the implementation.

External Formats

Currently only supported with the VK_ANDROID_external_memory_android_hardware_buffer extension. This extension allows Android applications to import implementation-defined external formats. There are many restrictions what are allowed with these external formats which are documented in the spec.

Tools

There are a few tools to help with getting all the information in a quick and in a human readable format.

vulkaninfo is a command line utility for Windows, Linux, and macOS that enables you to see all the available items listed above about your GPU. Refer to the Vulkaninfo documentation in the Vulkan SDK.

The Vulkan Hardware Capability Viewer app developed by Sascha Willems, is an Android app to display all details for devices that support Vulkan.