To copy regions of a source image into a destination image, potentially performing format conversion, arbitrary scaling, and filtering, call:
void vkCmdBlitImage(
VkCommandBuffer commandBuffer,
VkImage srcImage,
VkImageLayout srcImageLayout,
VkImage dstImage,
VkImageLayout dstImageLayout,
uint32_t regionCount,
const VkImageBlit* pRegions,
VkFilter filter);
commandBuffer is the command buffer into which the command will be
recorded.
srcImage is the source image.
srcImageLayout is the layout of the source image subresources for
the blit.
dstImage is the destination image.
dstImageLayout is the layout of the destination image subresources
for the blit.
regionCount is the number of regions to blit.
pRegions is a pointer to an array of VkImageBlit structures
specifying the regions to blit.
filter is a VkFilter specifying the filter to apply if the
blits require scaling.
vkCmdBlitImage must not be used for multisampled source or
destination images.
Use vkCmdResolveImage for this purpose.
As the sizes of the source and destination extents can differ in any dimension, texels in the source extent are scaled and filtered to the destination extent. Scaling occurs via the following operations:
For each destination texel, the integer coordinate of that texel is converted to an unnormalized texture coordinate, using the effective inverse of the equations described in unnormalized to integer conversion:
These base coordinates are then offset by the first destination offset:
baseArrayCountdst
The scale is determined from the source and destination regions, and applied to the offset coordinates:
Finally the source offset is added to the scaled coordinates, to
determine the final unnormalized coordinates used to sample from
srcImage:
mipLevel
baseArrayCountsrc
These coordinates are used to sample from the source image, as described in
Image Operations chapter, with the filter mode equal to that
of filter, a mipmap mode of VK_SAMPLER_MIPMAP_MODE_NEAREST and
an address mode of VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE.
Implementations must clamp at the edge of the source image, and may
additionally clamp to the edge of the source region.
| Note | |
|---|---|
Due to allowable rounding errors in the generation of the source texture coordinates, it is not always possible to guarantee exactly which source texels will be sampled for a given blit. As rounding errors are implementation dependent, the exact results of a blitting operation are also implementation dependent. |
Blits are done layer by layer starting with the baseArrayLayer member
of srcSubresource for the source and dstSubresource for the
destination.
layerCount layers are blitted to the destination image.
3D textures are blitted slice by slice.
Slices in the source region bounded by srcOffsets[0].z and
srcOffsets[1].z are copied to slices in the destination region
bounded by dstOffsets[0].z and dstOffsets[1].z.
For each destination slice, a source z coordinate is linearly interpolated
between srcOffsets[0].z and srcOffsets[1].z.
If the filter parameter is VK_FILTER_LINEAR then the value
sampled from the source image is taken by doing linear filtering using the
interpolated z coordinate.
If filter parameter is VK_FILTER_NEAREST then value sampled from
the source image is taken from the single nearest slice (with undefined
rounding mode).
The following filtering and conversion rules apply:
Signed and unsigned integers are converted by first clamping to the representable range of the destination format, then casting the value.
The VkImageBlit structure is defined as:
typedef struct VkImageBlit {
VkImageSubresourceLayers srcSubresource;
VkOffset3D srcOffsets[2];
VkImageSubresourceLayers dstSubresource;
VkOffset3D dstOffsets[2];
} VkImageBlit;
srcSubresource is the subresource to blit from.
srcOffsets is an array of two VkOffset3D structures
specifying the bounds of the source region within srcSubresource.
dstSubresource is the subresource to blit into.
dstOffsets is an array of two VkOffset3D structures
specifying the bounds of the destination region within
dstSubresource.
For each element of the pRegions array, a blit operation is performed
the specified source and destination regions.