rhi: Add support for separate image and sampler objects

For Direct 3D, Metal, and Vulkan this is natively supported. (and
makes no difference in particular for D3D and Metal because they do
not have the legacy combined image sampler concept anyways)

With OpenGL it will work too, but this relies on SPIR-Cross magic and
is still using a combined sampler (e.g. a sampler2D) in the GLSL
shader. The GL backend walks back and forth in the mapping tables from
the shader baker in order to make this work, which is presumably
slightly more expensive than combined image samplers.

Do note that combined image samplers (i.e. sampler2D in the shader and
QRhiShaderResourceBinding::sampledTexture() in code) continue to be
the primary, recommended way for any user of the rhi for the time
being.

Change-Id: I194721bc657b1ffbcc1bb79e6eadebe569a25087
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 127 insertions, 0 deletions

diff --git a/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp b/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
index 770d4be291..6a06fc4ef5 100644
--- a/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
+++ b/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
@@ -117,6 +117,8 @@ private slots:
     void renderToTextureTextureArray();
     void renderToTextureTexturedQuad_data();
     void renderToTextureTexturedQuad();
+    void renderToTextureSampleWithSeparateTextureAndSampler_data();
+    void renderToTextureSampleWithSeparateTextureAndSampler();
     void renderToTextureArrayOfTexturedQuad_data();
     void renderToTextureArrayOfTexturedQuad();
     void renderToTextureTexturedQuadAndUniformBuffer_data();
@@ -2157,6 +2159,131 @@ void tst_QRhi::renderToTextureTexturedQuad()
     QVERIFY(qGreen(result.pixel(214, 191)) > 2 * qBlue(result.pixel(214, 191)));
 }
 
+void tst_QRhi::renderToTextureSampleWithSeparateTextureAndSampler_data()
+{
+    rhiTestData();
+}
+
+void tst_QRhi::renderToTextureSampleWithSeparateTextureAndSampler()
+{
+    // Same as renderToTextureTexturedQuad but the fragment shader uses a
+    // separate image and sampler. For Vulkan/Metal/D3D11 these are natively
+    // supported. For OpenGL this exercises the auto-generated combined sampler
+    // in the GLSL code and the mapping table that gets applied at run time by
+    // the backend.
+
+    QFETCH(QRhi::Implementation, impl);
+    QFETCH(QRhiInitParams *, initParams);
+
+    QScopedPointer<QRhi> rhi(QRhi::create(impl, initParams, QRhi::Flags(), nullptr));
+    if (!rhi)
+        QSKIP("QRhi could not be created, skipping testing rendering");
+
+    QImage inputImage;
+    inputImage.load(QLatin1String(":/data/qt256.png"));
+    QVERIFY(!inputImage.isNull());
+
+    QScopedPointer<QRhiTexture> texture(rhi->newTexture(QRhiTexture::RGBA8, inputImage.size(), 1,
+                                                        QRhiTexture::RenderTarget | QRhiTexture::UsedAsTransferSource));
+    QVERIFY(texture->create());
+
+    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ texture.data() }));
+    QScopedPointer<QRhiRenderPassDescriptor> rpDesc(rt->newCompatibleRenderPassDescriptor());
+    rt->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(rt->create());
+
+    QRhiCommandBuffer *cb = nullptr;
+    QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
+    QVERIFY(cb);
+
+    QRhiResourceUpdateBatch *updates = rhi->nextResourceUpdateBatch();
+
+    QScopedPointer<QRhiBuffer> vbuf(rhi->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(quadVerticesUvs)));
+    QVERIFY(vbuf->create());
+    updates->uploadStaticBuffer(vbuf.data(), quadVerticesUvs);
+
+    QScopedPointer<QRhiTexture> inputTexture(rhi->newTexture(QRhiTexture::RGBA8, inputImage.size()));
+    QVERIFY(inputTexture->create());
+    updates->uploadTexture(inputTexture.data(), inputImage);
+
+    QScopedPointer<QRhiSampler> sampler(rhi->newSampler(QRhiSampler::Nearest, QRhiSampler::Nearest, QRhiSampler::None,
+                                                        QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge));
+    QVERIFY(sampler->create());
+
+    QScopedPointer<QRhiShaderResourceBindings> srb(rhi->newShaderResourceBindings());
+    srb->setBindings({
+                         QRhiShaderResourceBinding::texture(3, QRhiShaderResourceBinding::FragmentStage, inputTexture.data()),
+                         QRhiShaderResourceBinding::sampler(5, QRhiShaderResourceBinding::FragmentStage, sampler.data())
+                     });
+    QVERIFY(srb->create());
+
+    QScopedPointer<QRhiGraphicsPipeline> pipeline(rhi->newGraphicsPipeline());
+    pipeline->setTopology(QRhiGraphicsPipeline::TriangleStrip);
+    QShader vs = loadShader(":/data/simpletextured.vert.qsb");
+    QVERIFY(vs.isValid());
+    QShader fs = loadShader(":/data/simpletextured_separate.frag.qsb");
+    QVERIFY(fs.isValid());
+    pipeline->setShaderStages({ { QRhiShaderStage::Vertex, vs }, { QRhiShaderStage::Fragment, fs } });
+    QRhiVertexInputLayout inputLayout;
+    inputLayout.setBindings({ { 4 * sizeof(float) } });
+    inputLayout.setAttributes({
+                                  { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
+                                  { 0, 1, QRhiVertexInputAttribute::Float2, 2 * sizeof(float) }
+                              });
+    pipeline->setVertexInputLayout(inputLayout);
+    pipeline->setShaderResourceBindings(srb.data());
+    pipeline->setRenderPassDescriptor(rpDesc.data());
+
+    QVERIFY(pipeline->create());
+
+    cb->beginPass(rt.data(), Qt::black, { 1.0f, 0 }, updates);
+    cb->setGraphicsPipeline(pipeline.data());
+    cb->setShaderResources();
+    cb->setViewport({ 0, 0, float(texture->pixelSize().width()), float(texture->pixelSize().height()) });
+    QRhiCommandBuffer::VertexInput vbindings(vbuf.data(), 0);
+    cb->setVertexInput(0, 1, &vbindings);
+    cb->draw(4);
+
+    QRhiReadbackResult readResult;
+    QImage result;
+    readResult.completed = [&readResult, &result] {
+        result = QImage(reinterpret_cast<const uchar *>(readResult.data.constData()),
+                        readResult.pixelSize.width(), readResult.pixelSize.height(),
+                        QImage::Format_RGBA8888_Premultiplied);
+    };
+    QRhiResourceUpdateBatch *readbackBatch = rhi->nextResourceUpdateBatch();
+    readbackBatch->readBackTexture({ texture.data() }, &readResult);
+    cb->endPass(readbackBatch);
+
+    rhi->endOffscreenFrame();
+
+    QVERIFY(!result.isNull());
+
+    if (impl == QRhi::Null)
+        return;
+
+    if (rhi->isYUpInFramebuffer() != rhi->isYUpInNDC())
+        result = std::move(result).mirrored();
+
+    QRgb white = qRgba(255, 255, 255, 255);
+    QCOMPARE(result.pixel(79, 77), white);
+    QCOMPARE(result.pixel(124, 81), white);
+    QCOMPARE(result.pixel(128, 149), white);
+    QCOMPARE(result.pixel(120, 189), white);
+    QCOMPARE(result.pixel(116, 185), white);
+
+    QRgb empty = qRgba(0, 0, 0, 0);
+    QCOMPARE(result.pixel(11, 45), empty);
+    QCOMPARE(result.pixel(246, 202), empty);
+    QCOMPARE(result.pixel(130, 18), empty);
+    QCOMPARE(result.pixel(4, 227), empty);
+
+    QVERIFY(qGreen(result.pixel(32, 52)) > 2 * qRed(result.pixel(32, 52)));
+    QVERIFY(qGreen(result.pixel(32, 52)) > 2 * qBlue(result.pixel(32, 52)));
+    QVERIFY(qGreen(result.pixel(214, 191)) > 2 * qRed(result.pixel(214, 191)));
+    QVERIFY(qGreen(result.pixel(214, 191)) > 2 * qBlue(result.pixel(214, 191)));
+}
+
 void tst_QRhi::renderToTextureArrayOfTexturedQuad_data()
 {
     rhiTestData();