VkViewport

The VkViewport structure is defined as:

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

• 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.

The framebuffer depth coordinate z_f 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, …​, 2^m-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

• o_x = x + width / 2
• o_y = y + height / 2
• o_z = minDepth (or (maxDepth + minDepth) / 2 if VkPipelineViewportDepthClipControlCreateInfoEXT::negativeOneToOne is VK_TRUE)
• p_x = width
• p_y = height
• p_z = maxDepth - minDepth (or (maxDepth - minDepth) / 2 if VkPipelineViewportDepthClipControlCreateInfoEXT::negativeOneToOne is VK_TRUE)

If a render pass transform is enabled, the values (p_x,p_y) and (o_x, o_y) defining the viewport are transformed as described in render pass transform before participating in the viewport transform.

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 pre-rasterization shader stage.

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.