C Specification

The VkViewport structure is defined as:

typedef struct VkViewport {
    float    x;
    float    y;
    float    width;
    float    height;
    float    minDepth;
    float    maxDepth;
} VkViewport;

Members

  • x and y are the viewport’s upper left corner (x,y).

  • width and height are the viewport’s width and height, respectively.

  • minDepth and maxDepth are the depth range for the viewport. It is valid for minDepth to be greater than or equal to maxDepth.

Description

The framebuffer depth coordinate zf may be represented using either a fixed-point or floating-point representation. However, a floating-point representation must be used if the depth/stencil attachment has a floating-point depth component. If an m-bit fixed-point representation is used, we assume that it represents each value \(\frac{k}{2^m - 1}\), where k ∈ { 0, 1, …​, 2m-1 }, as k (e.g. 1.0 is represented in binary as a string of all ones).

The viewport parameters shown in the above equations are found from these values as

ox = x + width / 2

oy = y + height / 2

oz = minDepth

px = width

py = height

pz = maxDepth - minDepth.

The application can specify a negative term for height, which has the effect of negating the y coordinate in clip space before performing the transform. When using a negative height, the application should also adjust the y value to point to the lower left corner of the viewport instead of the upper left corner. Using the negative height allows the application to avoid having to negate the y component of the Position output from the last vertex processing stage in shaders that also target other graphics APIs.

The width and height of the implementation-dependent maximum viewport dimensions must be greater than or equal to the width and height of the largest image which can be created and attached to a framebuffer.

The floating-point viewport bounds are represented with an implementation-dependent precision.

Valid Usage
  • width must be greater than 0.0

  • width must be less than or equal to VkPhysicalDeviceLimits::maxViewportDimensions[0]

  • The absolute value of height must be less than or equal to VkPhysicalDeviceLimits::maxViewportDimensions[1]

  • x must be greater than or equal to viewportBoundsRange[0]

  • (x + width) must be less than or equal to viewportBoundsRange[1]

  • y must be greater than or equal to viewportBoundsRange[0]

  • y must be less than or equal to viewportBoundsRange[1]

  • (y + height) must be greater than or equal to viewportBoundsRange[0]

  • (y + height) must be less than or equal to viewportBoundsRange[1]

  • Unless ../../html/vkspec.html#VK_EXT_depth_range_unrestricted extension is enabled minDepth must be between 0.0 and 1.0, inclusive

  • Unless ../../html/vkspec.html#VK_EXT_depth_range_unrestricted extension is enabled maxDepth must be between 0.0 and 1.0, inclusive

See Also

Document Notes

For more information, see the Vulkan Specification at URL

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

Copyright (c) 2014-2018 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.