This extension adds support for a new image organization, which this extension refers to as “corner-sampled” images. A corner-sampled image differs from a conventional image in the following ways:

• Texels are centered on integer coordinates. See Unnormalized Texel Coordinate Operations
• Normalized coordinates are scaled using coord × (dim - 1) rather than coord × dim, where dim is the size of one dimension of the image. See normalized texel coordinate transform.
• Partial derivatives are scaled using coord × (dim - 1) rather than coord × dim. See Scale Factor Operation.
• Calculation of the next higher LOD size goes according to ⌈dim / 2⌉ rather than ⌊dim / 2⌋. See Image Mip Level Sizing.
• The minimum level size is 2x2 for 2D images and 2x2x2 for 3D images. See Image Mip Level Sizing.

This image organization is designed to facilitate a system like Ptex with separate textures for each face of a subdivision or polygon mesh. Placing sample locations at pixel corners allows applications to maintain continuity between adjacent patches by duplicating values along shared edges. Additionally, using the modified mipmapping logic along with texture dimensions of the form 2n+1 allows continuity across shared edges even if the adjacent patches use different LOD values.

VK_NV_corner_sampled_image

Name String

VK_NV_corner_sampled_image

Extension Type

Device extension

Registered Extension Number

51

Revision

2

Extension and Version Dependencies

VK_KHR_get_physical_device_properties2

Contact

• Daniel Koch dgkoch

Other Extension Metadata

Last Modified Date

2018-08-13

Contributors

• Jeff Bolz, NVIDIA
• Pat Brown, NVIDIA
• Chris Lentini, NVIDIA