C Specification

An acceleration structure SRT transform is defined by the structure:

// Provided by VK_NV_ray_tracing_motion_blur
typedef struct VkSRTDataNV {
    float    sx;
    float    a;
    float    b;
    float    pvx;
    float    sy;
    float    c;
    float    pvy;
    float    sz;
    float    pvz;
    float    qx;
    float    qy;
    float    qz;
    float    qw;
    float    tx;
    float    ty;
    float    tz;
} VkSRTDataNV;

Members

  • sx is the x component of the scale of the transform

  • a is one component of the shear for the transform

  • b is one component of the shear for the transform

  • pvx is the x component of the pivot point of the transform

  • sy is the y component of the scale of the transform

  • c is one component of the shear for the transform

  • pvy is the y component of the pivot point of the transform

  • sz is the z component of the scale of the transform

  • pvz is the z component of the pivot point of the transform

  • qx is the x component of the rotation quaternion

  • qy is the y component of the rotation quaternion

  • qz is the z component of the rotation quaternion

  • qw is the w component of the rotation quaternion

  • tx is the x component of the post-rotation translation

  • ty is the y component of the post-rotation translation

  • tz is the z component of the post-rotation translation

Description

This transform decomposition consists of three elements. The first is a matrix S, consisting of a scale, shear, and translation, usually used to define the pivot point of the following rotation. This matrix is constructed from the parameters above by:

The rotation quaternion is defined as:

R = [ qx, qy, qz, qw ]

This is a rotation around a conceptual normalized axis [ ax, ay, az ] of amount theta such that:

[ qx, qy, qz ] = sin(theta/2) × [ ax, ay, az ]

and

qw = cos(theta/2)

Finally, the transform has a translation T constructed from the parameters above by:

The effective derived transform is then given by

T × R × S

See Also

VK_NV_ray_tracing_motion_blur, VkAccelerationStructureSRTMotionInstanceNV

Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

Copyright

Copyright 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0