QRhiTextureUploadDescription Class

Describes a texture upload operation. More...

Header: #include <QRhiTextureUploadDescription>
CMake: find_package(Qt6 REQUIRED COMPONENTS Gui)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: QT += gui
Since: Qt 6.6

Public Functions

QRhiTextureUploadDescription(const QRhiTextureUploadEntry &entry)
QRhiTextureUploadDescription(std::initializer_list<QRhiTextureUploadEntry> list)
const QRhiTextureUploadEntry *cbeginEntries() const
const QRhiTextureUploadEntry *cendEntries() const
const QRhiTextureUploadEntry *entryAt(qsizetype index) const
qsizetype entryCount() const
void setEntries(std::initializer_list<QRhiTextureUploadEntry> list)
void setEntries(InputIterator first, InputIterator last)

Detailed Description

Used with QRhiResourceUpdateBatch::uploadTexture(). That function has two variants: one taking a QImage and one taking a QRhiTextureUploadDescription. The former is a convenience version, internally creating a QRhiTextureUploadDescription with a single image targeting level 0 for layer 0.

An example of the the common, simple case of wanting to upload the contents of a QImage to a QRhiTexture with a matching pixel size:

QImage image(256, 256, QImage::Format_RGBA8888);
image.fill(Qt::green); // or could use a QPainter targeting image
QRhiTexture *texture = rhi->newTexture(QRhiTexture::RGBA8, QSize(256, 256));
QRhiResourceUpdateBatch *u = rhi->nextResourceUpdateBatch();
u->uploadTexture(texture, image);

When cubemaps, pre-generated mip images, compressed textures, or partial uploads are involved, applications will have to use this class instead.

QRhiTextureUploadDescription also enables specifying batched uploads, which are useful for example when generating an atlas or glyph cache texture: multiple, partial uploads for the same subresource (meaning the same layer and level) are supported, and can be, depending on the backend and the underlying graphics API, more efficient when batched into the same QRhiTextureUploadDescription as opposed to issuing individual uploadTexture() commands for each of them.

Note: Cubemaps have one layer for each of the six faces in the order +X, -X, +Y, -Y, +Z, -Z.

For example, specifying the faces of a cubemap could look like the following:

QImage faces[6];
// ...
QVarLengthArray<QRhiTextureUploadEntry, 6> entries;
for (int i = 0; i < 6; ++i)
  entries.append(QRhiTextureUploadEntry(i, 0, faces[i]));
QRhiTextureUploadDescription desc;
desc.setEntries(entries.cbegin(), entries.cend());
resourceUpdates->uploadTexture(texture, desc);

Another example that specifies mip images for a compressed texture:

QList<QRhiTextureUploadEntry> entries;
const int mipCount = rhi->mipLevelsForSize(compressedTexture->pixelSize());
for (int level = 0; level < mipCount; ++level) {
    const QByteArray compressedDataForLevel = ..
    entries.append(QRhiTextureUploadEntry(0, level, compressedDataForLevel));
QRhiTextureUploadDescription desc;
desc.setEntries(entries.cbegin(), entries.cend());
resourceUpdates->uploadTexture(compressedTexture, desc);

With partial uploads targeting the same subresource, it is recommended to batch them into a single upload request, whenever possible:

QRhiTextureSubresourceUploadDescription subresDesc(image);
subresDesc.setSourceSize(QSize(10, 10));
subResDesc.setDestinationTopLeft(QPoint(50, 40));
QRhiTextureUploadEntry entry(0, 0, subresDesc); // layer 0, level 0

QRhiTextureSubresourceUploadDescription subresDesc2(image);
subresDesc2.setSourceSize(QSize(30, 40));
subResDesc2.setDestinationTopLeft(QPoint(100, 200));
QRhiTextureUploadEntry entry2(0, 0, subresDesc2); // layer 0, level 0, i.e. same subresource

QRhiTextureUploadDescription desc({ entry, entry2});
resourceUpdates->uploadTexture(texture, desc);

Note: This is a RHI API with limited compatibility guarantees, see QRhi for details.

See also QRhiResourceUpdateBatch.

Member Function Documentation

[constexpr noexcept] QRhiTextureUploadDescription::QRhiTextureUploadDescription()

Constructs an empty texture upload description.

QRhiTextureUploadDescription::QRhiTextureUploadDescription(const QRhiTextureUploadEntry &entry)

Constructs a texture upload description with a single subresource upload described by entry.

QRhiTextureUploadDescription::QRhiTextureUploadDescription(std::initializer_list<QRhiTextureUploadEntry> list)

Constructs a texture upload description with the specified list of entries.

Note: list can also contain multiple QRhiTextureUploadEntry elements with the same layer and level. This makes sense when those uploads are partial, meaning their subresource description has a source size or image smaller than the subresource dimensions, and can be more efficient than issuing separate uploadTexture()'s.

const QRhiTextureUploadEntry *QRhiTextureUploadDescription::cbeginEntries() const

Returns a const iterator pointing to the first item in the entry list.

const QRhiTextureUploadEntry *QRhiTextureUploadDescription::cendEntries() const

Returns a const iterator pointing just after the last item in the entry list.

const QRhiTextureUploadEntry *QRhiTextureUploadDescription::entryAt(qsizetype index) const

Returns the entry at index.

qsizetype QRhiTextureUploadDescription::entryCount() const

Returns the number of entries.

void QRhiTextureUploadDescription::setEntries(std::initializer_list<QRhiTextureUploadEntry> list)

Sets the list of entries.

template <typename InputIterator> void QRhiTextureUploadDescription::setEntries(InputIterator first, InputIterator last)

Sets the list of entries using the iterators first and last.

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