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Qt
Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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Qt
Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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\variable QRhiDispatchIndirectCommand::x More...
#include <qrhi.h>
Public Types | |
| enum | Type { Draws , IndexedDraws } |
| Specifies the kind of commands an indirect command buffer holds. More... | |
| Public Types inherited from QRhiResource | |
| enum | Type { Buffer , Texture , Sampler , RenderBuffer , RenderPassDescriptor , SwapChainRenderTarget , TextureRenderTarget , ShaderResourceBindings , GraphicsPipeline , SwapChain , ComputePipeline , CommandBuffer , ShadingRateMap , IndirectCommandBuffer } |
| Specifies type of the resource. More... | |
Public Member Functions | |
| QRhiResource::Type | resourceType () const override |
| Type | type () const |
| void | setType (Type t) |
| Sets the command type t. | |
| quint32 | maxCommandCount () const |
| void | setMaxCommandCount (quint32 count) |
| Sets the capacity, the maximum number of commands, to count. | |
| virtual bool | create ()=0 |
| Creates the corresponding native objects. | |
| void | clear () |
| Discards all commands recorded so far. | |
| void | draw (quint32 vertexCount, quint32 instanceCount=1, quint32 firstVertex=0, quint32 firstInstance=0) |
| Records a non-indexed draw command with vertexCount, instanceCount, firstVertex, and firstInstance. | |
| void | drawIndexed (quint32 indexCount, quint32 instanceCount=1, quint32 firstIndex=0, qint32 vertexOffset=0, quint32 firstInstance=0) |
| Records an indexed draw command with indexCount, instanceCount, firstIndex, vertexOffset, and firstInstance. | |
| quint32 | recordedCommandCount () const |
| bool | isGpuBuilt () const |
| quint32 | commandCount () const |
| Public Member Functions inherited from QRhiResource | |
| virtual | ~QRhiResource () |
| Destructor. | |
| virtual void | destroy ()=0 |
| Releases (or requests deferred releasing of) the underlying native graphics resources. | |
| void | deleteLater () |
| When called without a frame being recorded, this function is equivalent to deleting the object. | |
| QByteArray | name () const |
| void | setName (const QByteArray &name) |
| Sets a name for the object. | |
| quint64 | globalResourceId () const |
| QRhi * | rhi () const |
Protected Member Functions | |
| QRhiIndirectCommandBuffer (QRhiImplementation *rhi, Type type_, quint32 maxCommandCount_) | |
| Protected Member Functions inherited from QRhiResource | |
| QRhiResource (QRhiImplementation *rhi) | |
Protected Attributes | |
| Type | m_type |
| quint32 | m_maxCommandCount |
| QByteArray | m_data |
| quint32 | m_commandCount = 0 |
| quint64 | m_generation = 0 |
| bool | m_gpuBuilt = false |
| quint32 | m_gpuBuiltCommandCount = 0 |
| Protected Attributes inherited from QRhiResource | |
| QRhiImplementation * | m_rhi = nullptr |
| quint64 | m_id |
| QByteArray | m_objectName |
\variable QRhiDispatchIndirectCommand::x
\variable QRhiDispatchIndirectCommand::y
\variable QRhiDispatchIndirectCommand::z
\inmodule QtGuiPrivate \inheaderfile rhi/qrhi.h
A prerecorded batch of indirect draw commands.
A QRhiIndirectCommandBuffer holds a number of draw commands that are recorded once and can then be replayed any number of times with a single QRhiCommandBuffer::executeIndirect() call. It is an alternative to the buffer-based QRhiCommandBuffer::drawIndirect() family of functions. Under the hood, it may do exactly the same as does (typical with Vulkan, Direct 3D, and OpenGL), or may be implemented differently (Metal).
Create one with QRhi::newIndirectCommandBuffer(), passing in the type and the maximum number of commands, and call create(). The (maximum) command count is mandatory, whichever way the commands are going to be provided: it is the capacity of the object, and create() fails when it is 0.
\badcode icb = rhi->newIndirectCommandBuffer(QRhiIndirectCommandBuffer::IndexedDraws, 1024); if (!icb->create()) { error(); }
Record commands with draw() or drawIndexed(), then hand the object to a resource update batch so that the recorded contents reach the GPU. commitIndirectCommandBuffer() has to be called after recording and before the pass that executes the commands. It is a no-op when nothing changed since the last time, so calling it every frame is cheap.
Executing happens inside a render pass:
\badcode icb->clear(); for (const Item &item : items) icb->drawIndexed(item.indexCount, 1, item.firstIndex, item.vertexOffset);
QRhiResourceUpdateBatch *u = rhi->nextResourceUpdateBatch(); u->commitIndirectCommandBuffer(icb);
cb->beginPass(rt, Qt::black, { 1.0f, 0 }, u); cb->setGraphicsPipeline(ps); cb->setVertexInput(0, 1, &vbufBinding, ibuf, 0, QRhiCommandBuffer::IndexUInt16); cb->setShaderResources(); cb->executeIndirect(icb); cb->endPass();
The commands can also be generated on the GPU instead of being recorded on the CPU. In that case fill a buffer with QRhiIndirectDrawCommand or QRhiIndexedIndirectDrawCommand entries from a compute shader, and call QRhiCommandBuffer::buildIndirect() with that buffer. That call must happen outside of any pass. The CPU-side recording functions of QRhiIndirectCommandBuffer are not used in this case.
\badcode cb->beginComputePass(); ... // a cb->dispatch() to invoke a compute shader that writes to indirectBuf cb->endComputePass();
QRhiIndirectCommandBufferBuildInfo buildInfo; buildInfo.topology = ps->topology(); buildInfo.sourceBuffer = indirectBuf; buildInfo.commandCount = itemCount; // as many as the compute shader wrote buildInfo.indexBuffer = indexBuffer; buildInfo.indexFormat = QRhiCommandBuffer::IndexUInt16; cb->buildIndirect(icb, buildInfo);
cb->beginPass(rt, Qt::black, { 1.0f, 0 }); cb->setGraphicsPipeline(ps); cb->setVertexInput(0, 1, &vbufBinding, ibuf, 0, QRhiCommandBuffer::IndexUInt16); cb->setShaderResources(); cb->executeIndirect(icb); cb->endPass();
When the number of commands is itself decided on the device, set QRhiIndirectCommandBufferBuildInfo::countBuffer instead of working out itemCount on the CPU. See \l{Command counts} below.
Specifies the kind of commands an indirect command buffer holds.
\value Draws Non-indexed draw commands, recorded with draw(). \value IndexedDraws Indexed draw commands, recorded with drawIndexed().
| Enumerator | |
|---|---|
| Draws | |
| IndexedDraws | |
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| void QRhiIndirectCommandBuffer::clear | ( | ) |
Discards all commands recorded so far.
Can be called at any time, also before create(). The recorded contents only become visible to the GPU once the object is passed to QRhiResourceUpdateBatch::commitIndirectCommandBuffer().
This resets recordedCommandCount() to 0. It does not undo a QRhiCommandBuffer::buildIndirect(): an indirect command buffer that gets its commands from the GPU keeps doing so, and commandCount() is unchanged.
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This is recordedCommandCount() for a CPU-recorded indirect command buffer, and the count resolved from QRhiIndirectCommandBufferBuildInfo::commandCount once QRhiCommandBuffer::buildIndirect() has been called.
A count buffer, if there is one, can reduce the number of draws further at execution time. This function does not, and cannot, account for that.
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pure virtual |
Creates the corresponding native objects.
Fails when maxCommandCount() is 0.
A given QRhiIndirectCommandBuffer takes its commands either from draw() and drawIndexed() followed by QRhiResourceUpdateBatch::commitIndirectCommandBuffer(), or from QRhiCommandBuffer::buildIndirect(), but not from both. Moving to the latter is one-way: clear() does not undo it, and neither does a subsequent commitIndirectCommandBuffer(); isGpuBuilt() stays true and the commands keep coming from the buffer. Call create() again to get an indirect command buffer that is populated from the CPU once more.
true when successful, false when a graphics operation failed. Implemented in QMetalIndirectCommandBuffer, and QRhiBufferBackedIndirectCommandBuffer.
| void QRhiIndirectCommandBuffer::draw | ( | quint32 | vertexCount, |
| quint32 | instanceCount = 1, | ||
| quint32 | firstVertex = 0, | ||
| quint32 | firstInstance = 0 ) |
Records a non-indexed draw command with vertexCount, instanceCount, firstVertex, and firstInstance.
The semantics are the same as QRhiCommandBuffer::draw().
| void QRhiIndirectCommandBuffer::drawIndexed | ( | quint32 | indexCount, |
| quint32 | instanceCount = 1, | ||
| quint32 | firstIndex = 0, | ||
| qint32 | vertexOffset = 0, | ||
| quint32 | firstInstance = 0 ) |
Records an indexed draw command with indexCount, instanceCount, firstIndex, vertexOffset, and firstInstance.
The semantics are the same as QRhiCommandBuffer::drawIndexed().
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true when QRhiCommandBuffer::buildIndirect() has been called on this indirect command buffer, meaning its contents come from a QRhiBuffer instead of from draw() and drawIndexed().Once true, this stays true until the next create().
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This is unaffected by QRhiCommandBuffer::buildIndirect(): once the commands come from the GPU, whatever was recorded on the CPU is ignored. Use commandCount() to get the number of commands that will actually be executed.
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Sets the capacity, the maximum number of commands, to count.
The capacity is normally specified in QRhi::newIndirectCommandBuffer(), so this function is only used when it has to be changed. As with other setters, it only takes effect when calling create(), which fails when count is 0.
The capacity applies regardless of how the commands are going to be provided: recording them with draw() and drawIndexed() and building them with QRhiCommandBuffer::buildIndirect() are both bounded by it.
draw() and drawIndexed() ignore, with a warning, any command past the first count ones. QRhiCommandBuffer::buildIndirect() clamps, also with a warning, when QRhiIndirectCommandBufferBuildInfo::commandCount is larger.
Sets the command type t.
The type is normally specified in QRhi::newIndirectCommandBuffer(), so this function is only used when it has to be changed. As with other setters, it only takes effect when calling create().
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1.16.1