CODEWITHSUNDEEP
vulkan
Andrew Tomazos
Andrew Tomazos

Reputation: 68728

Calculating VkImageAspectFlagsBits from VkImageCreateInfo?

Under Appendix H of the Vulkan spec it says:

Aspect (Image):

An image may contain multiple kinds, or aspects, of data for each pixel, where each aspect is used in a particular way by the pipeline and may be stored differently or separately from other aspects. For example, the color components of an image format make up the color aspect of the image, and may be used as a framebuffer color attachment. Some operations, like depth testing, operate only on specific aspects of an image. Others operations, like image/buffer copies, only operate on one aspect at a time.

In addition there is the type VkImageAspectFlagBits which (I think) lists the 7 possible aspects an image can have:

VK_IMAGE_ASPECT_COLOR_BIT
VK_IMAGE_ASPECT_DEPTH_BIT
VK_IMAGE_ASPECT_STENCIL_BIT
VK_IMAGE_ASPECT_METADATA_BIT
VK_IMAGE_ASPECT_PLANE_0_BIT
VK_IMAGE_ASPECT_PLANE_1_BIT
VK_IMAGE_ASPECT_PLANE_2_BIT

VkImageCreateInfo does not have an aspects field.

If I understand correctly, a given VkImage has a subset of these 7 aspects, right?

Is there a way to deduce which of the 7 aspects a VkImage has from its VkImageCreateInfo?

ie how would you write a function that returns a bit mask of which aspects an image has?

VkImageAspectFlagsBits GetImageAspects(const VkImageCreateInfo& info) { ??? }

Upvotes: 1

Views: 503

Answers (1)

Jesse Hall
Jesse Hall

Reputation: 6807

You can mostly derive which aspects an image has from its format:

  • VK_IMAGE_ASPECT_COLOR_BIT refers to all R, G, B, and/or A components available in the format.
  • VK_IMAGE_ASPECT_DEPTH_BIT refers to D components.
  • VK_IMAGE_ASPECT_STENCIL_BIT refers to S components.
  • VK_IMAGE_ASPECT_PLANE_n_BIT refer to the planes of multi-planar formats, i.e. ones with 2PLANE or 3PLANE in their name. These aspects are mostly used in copy commands, but can also be used to create a VkImageView of an individual plane rather than the whole image.
  • VK_IMAGE_ASPECT_METADATA_BIT is the odd one whose presence isn't based on format. Instead, images with sparse residency (VK_IMAGE_CREATE_SPARSE_RESIDENCY_BIT) have a metadata aspect.

If an image doesn't have the components or flag corresponding to the aspect, then it doesn't have that aspect.

Upvotes: 1

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