VK_EXT_image_2d_array_of_3d
This document proposes adding support for creating 2D views of 3D images.
1. Problem Statement
Other graphics APIs, such as OpenGL, provide functionality for creating two dimensional views of three dimensional images for use in shaders. When performing similar operations in Vulkan, this functionality may be emulated in shaders, but many implementations are capable of handling it at the execution level to avoid needing more shader variants or uniform or push constant data.
This proposal aims to provide this functionality.
2. Solution Space
This functionality could alternatively be emulated with: . Shader variants which each access the intended slice of the 3D image . The use of either uniform or push constant data to dynamically access the intended slice of the 3D image
Neither of these methods solves the more fundamental problem of having an API mismatch which complicates both transitioning from OpenGL to Vulkan and emulating OpenGL on Vulkan.
3. Proposal
3.1. API Features
The following features are exposed by this extension:
typedef struct VkPhysicalDeviceImage2DViewOf3DFeaturesEXT {
VkStructureType sType;
void* pNext;
VkBool32 image2DViewOf3D;
VkBool32 sampler2DViewOf3D;
} VkPhysicalDeviceImage2DViewOf3DFeaturesEXT;image2DViewOf3D is the core feature enabling this extension’s functionality.
sampler2DViewOf3D indicates that the driver supports 2D views of 3D textures.
Using the VK_IMAGE_CREATE_2D_VIEW_COMPATIBLE_BIT_EXT flag when creating a 3D image enables this functionality for that image.
4. Examples
As an example, if an application creates a VkImage of type VK_IMAGE_TYPE_3D with two layers and wants to only access the zero-th layer in a shader, VK_IMAGE_CREATE_2D_VIEW_COMPATIBLE_BIT_EXT can be used to create the image. A VkImageView is then created with VK_IMAGE_VIEW_TYPE_2D, and the shader can then access the image data using two-dimensional image operations.