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// Copyright (C) 2019 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#include "../shared/examplefw.h"
#include <QRandomGenerator>
// Compute shader example. Writes to a storage buffer from a compute shader,
// then uses the same buffer as vertex buffer in the vertex stage. This would
// be typical when implementing particles for example. Here we just simply move
// the positions back and forth along the X axis.
// Note that the example relies on gl_PointSize which is not supported
// everywhere. So in some cases the points will be of size 1.
struct {
QList<QRhiResource *> releasePool;
QRhiBuffer *sbuf = nullptr;
QRhiBuffer *computeUniBuf = nullptr;
QRhiShaderResourceBindings *computeBindings = nullptr;
QRhiComputePipeline *computePipeline = nullptr;
QRhiShaderResourceBindings *graphicsBindings = nullptr;
QRhiGraphicsPipeline *graphicsPipeline = nullptr;
QRhiResourceUpdateBatch *initialUpdates = nullptr;
float step = 0.2f;
} d;
// these struct must match the std140 packing rules
struct Data {
float pos[2];
float dir;
quint32 pad[1];
};
struct ComputeUBuf {
float step;
quint32 count;
};
const int DATA_COUNT = 256 * 128;
const int COMPUTE_UBUF_SIZE = 8;
void Window::customInit()
{
if (!m_r->isFeatureSupported(QRhi::Compute))
qFatal("Compute is not supported");
if (!m_r->isFeatureSupported(QRhi::VertexShaderPointSize))
qWarning("Point sizes other than 1 not supported");
// compute pass
d.sbuf = m_r->newBuffer(QRhiBuffer::Immutable,
QRhiBuffer::StorageBuffer | QRhiBuffer::VertexBuffer,
sizeof(Data) * DATA_COUNT);
d.sbuf->create();
d.releasePool << d.sbuf;
d.computeUniBuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, COMPUTE_UBUF_SIZE);
d.computeUniBuf->create();
d.releasePool << d.computeUniBuf;
d.initialUpdates = m_r->nextResourceUpdateBatch();
QByteArray data;
data.resize(sizeof(Data) * DATA_COUNT);
Data *p = reinterpret_cast<Data *>(data.data());
QRandomGenerator *rgen = QRandomGenerator::global();
for (int i = 0; i < DATA_COUNT; ++i) {
p->pos[0] = rgen->bounded(1000) / 500.0f - 1.0f;
p->pos[1] = rgen->bounded(1000) / 500.0f - 1.0f;
p->dir = rgen->bounded(2) ? 1 : -1;
++p;
}
d.initialUpdates->uploadStaticBuffer(d.sbuf, data.constData());
ComputeUBuf ud;
ud.step = d.step;
ud.count = DATA_COUNT;
d.initialUpdates->updateDynamicBuffer(d.computeUniBuf, 0, COMPUTE_UBUF_SIZE, &ud);
d.computeBindings = m_r->newShaderResourceBindings();
d.computeBindings->setBindings({
QRhiShaderResourceBinding::bufferLoadStore(0, QRhiShaderResourceBinding::ComputeStage, d.sbuf),
QRhiShaderResourceBinding::uniformBuffer(1, QRhiShaderResourceBinding::ComputeStage, d.computeUniBuf)
});
d.computeBindings->create();
d.releasePool << d.computeBindings;
d.computePipeline = m_r->newComputePipeline();
d.computePipeline->setShaderResourceBindings(d.computeBindings);
d.computePipeline->setShaderStage({ QRhiShaderStage::Compute, getShader(QLatin1String(":/buffer.comp.qsb")) });
d.computePipeline->create();
d.releasePool << d.computePipeline;
// graphics pass
d.graphicsBindings = m_r->newShaderResourceBindings();
d.graphicsBindings->create();
d.releasePool << d.graphicsBindings;
d.graphicsPipeline = m_r->newGraphicsPipeline();
d.graphicsPipeline->setTopology(QRhiGraphicsPipeline::Points);
d.graphicsPipeline->setShaderStages({
{ QRhiShaderStage::Vertex, getShader(QLatin1String(":/main.vert.qsb")) },
{ QRhiShaderStage::Fragment, getShader(QLatin1String(":/main.frag.qsb")) }
});
QRhiVertexInputLayout inputLayout;
inputLayout.setBindings({
{ 2 * sizeof(float) }
});
inputLayout.setAttributes({
{ 0, 0, QRhiVertexInputAttribute::Float2, 0 },
});
d.graphicsPipeline->setVertexInputLayout(inputLayout);
d.graphicsPipeline->setShaderResourceBindings(d.graphicsBindings);
d.graphicsPipeline->setRenderPassDescriptor(m_rp);
d.graphicsPipeline->create();
d.releasePool << d.graphicsPipeline;
}
void Window::customRelease()
{
qDeleteAll(d.releasePool);
d.releasePool.clear();
}
void Window::customRender()
{
const QSize outputSizeInPixels = m_sc->currentPixelSize();
QRhiCommandBuffer *cb = m_sc->currentFrameCommandBuffer();
QRhiResourceUpdateBatch *u = m_r->nextResourceUpdateBatch();
if (d.initialUpdates) {
u->merge(d.initialUpdates);
d.initialUpdates->release();
d.initialUpdates = nullptr;
}
#if 0
u->updateDynamicBuffer(d.computeUniBuf, 0, sizeof(float), &d.step);
d.step += 0.01f;
#endif
// compute pass
cb->beginComputePass(u);
cb->setComputePipeline(d.computePipeline);
cb->setShaderResources();
cb->dispatch(DATA_COUNT / 256, 1, 1);
cb->endComputePass();
// graphics pass
cb->beginPass(m_sc->currentFrameRenderTarget(), m_clearColor, { 1.0f, 0 });
cb->setGraphicsPipeline(d.graphicsPipeline);
cb->setViewport({ 0, 0, float(outputSizeInPixels.width()), float(outputSizeInPixels.height()) });
QRhiCommandBuffer::VertexInput vbufBinding(d.sbuf, 0);
cb->setVertexInput(0, 1, &vbufBinding);
cb->draw(DATA_COUNT);
cb->endPass();
}
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