Enhance rendernode example with opacity support

The opacity is already animated in the QML scene but enabling
blending and using inheritedOpacity() was not done. Until now.

Change-Id: Iaaf50c20302e29db85c5dfaeaab4d069cb18714e
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

5 files changed, 49 insertions, 22 deletions

diff --git a/examples/quick/scenegraph/rendernode/d3d12renderer.cpp b/examples/quick/scenegraph/rendernode/d3d12renderer.cpp
index 3694c6ae75..bc03720407 100644
--- a/examples/quick/scenegraph/rendernode/d3d12renderer.cpp
+++ b/examples/quick/scenegraph/rendernode/d3d12renderer.cpp
@@ -83,7 +83,7 @@ void D3D12RenderNode::init()
 
     D3D12_ROOT_PARAMETER rootParameter;
     rootParameter.ParameterType = D3D12_ROOT_PARAMETER_TYPE_CBV;
-    rootParameter.ShaderVisibility = D3D12_SHADER_VISIBILITY_VERTEX;
+    rootParameter.ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL;
     rootParameter.Descriptor.ShaderRegister = 0; // b0
     rootParameter.Descriptor.RegisterSpace = 0;
 
@@ -123,11 +123,19 @@ void D3D12RenderNode::init()
     rastDesc.CullMode = D3D12_CULL_MODE_BACK;
     rastDesc.FrontCounterClockwise = TRUE; // Vertices are given CCW
 
-    // No blending, just enable color write.
-    D3D12_RENDER_TARGET_BLEND_DESC defaultRenderTargetBlendDesc = {};
-    defaultRenderTargetBlendDesc.RenderTargetWriteMask = D3D12_COLOR_WRITE_ENABLE_ALL;
+    // Enable color write and blending (premultiplied alpha). The latter is
+    // needed because the example changes the item's opacity and we pass
+    // inheritedOpacity() into the pixel shader. If that wasn't the case,
+    // blending could have stayed disabled.
+    const D3D12_RENDER_TARGET_BLEND_DESC premulBlendDesc = {
+        TRUE, FALSE,
+        D3D12_BLEND_ONE, D3D12_BLEND_INV_SRC_ALPHA, D3D12_BLEND_OP_ADD,
+        D3D12_BLEND_ONE, D3D12_BLEND_INV_SRC_ALPHA, D3D12_BLEND_OP_ADD,
+        D3D12_LOGIC_OP_NOOP,
+        D3D12_COLOR_WRITE_ENABLE_ALL
+    };
     D3D12_BLEND_DESC blendDesc = {};
-    blendDesc.RenderTarget[0] = defaultRenderTargetBlendDesc;
+    blendDesc.RenderTarget[0] = premulBlendDesc;
 
     D3D12_GRAPHICS_PIPELINE_STATE_DESC psoDesc = {};
     psoDesc.InputLayout = { inputElementDescs, _countof(inputElementDescs) };
@@ -177,7 +185,7 @@ void D3D12RenderNode::init()
     }
 
     vertexBufferView.BufferLocation = vertexBuffer->GetGPUVirtualAddress();
-    vertexBufferView.StrideInBytes = (2 + 3) * sizeof(float);
+    vertexBufferView.StrideInBytes = vertexBufferSize / 3;
     vertexBufferView.SizeInBytes = vertexBufferSize;
 
     bufDesc.Width = 256;
@@ -198,6 +206,14 @@ void D3D12RenderNode::init()
         qWarning("Map failed (constant buffer)");
         return;
     }
+
+    float *vp = reinterpret_cast<float *>(vbPtr);
+    vp += 2;
+    *vp++ = 1.0f; *vp++ = 0.0f; *vp++ = 0.0f;
+    vp += 2;
+    *vp++ = 0.0f; *vp++ = 1.0f; *vp++ = 0.0f;
+    vp += 2;
+    *vp++ = 0.0f; *vp++ = 0.0f; *vp++ = 1.0f;
 }
 
 void D3D12RenderNode::render(const RenderState *state)
@@ -212,6 +228,8 @@ void D3D12RenderNode::render(const RenderState *state)
     const int msize = 16 * sizeof(float);
     memcpy(cbPtr, matrix()->constData(), msize);
     memcpy(cbPtr + msize, state->projectionMatrix()->constData(), msize);
+    const float opacity = inheritedOpacity();
+    memcpy(cbPtr + 2 * msize, &opacity, sizeof(float));
 
     const QPointF p0(m_item->width() - 1, m_item->height() - 1);
     const QPointF p1(0, 0);
@@ -220,15 +238,12 @@ void D3D12RenderNode::render(const RenderState *state)
     float *vp = reinterpret_cast<float *>(vbPtr);
     *vp++ = p0.x();
     *vp++ = p0.y();
-    *vp++ = 1.0f; *vp++ = 0.0f; *vp++ = 0.0f;
-
+    vp += 3;
     *vp++ = p1.x();
     *vp++ = p1.y();
-    *vp++ = 0.0f; *vp++ = 1.0f; *vp++ = 0.0f;
-
+    vp += 3;
     *vp++ = p2.x();
     *vp++ = p2.y();
-    *vp++ = 0.0f; *vp++ = 0.0f; *vp++ = 1.0f;
 
     commandList->SetPipelineState(pipelineState.Get());
     commandList->SetGraphicsRootSignature(rootSignature.Get());
@@ -237,8 +252,9 @@ void D3D12RenderNode::render(const RenderState *state)
     commandList->IASetVertexBuffers(0, 1, &vertexBufferView);
 
     commandList->DrawInstanced(3, 1, 0, 0);
-
-    // we won't implement changedStates() since no viewport/scissor/stencil/blend related commands were added
 }
 
+// No need to reimplement changedStates() because no relevant commands are
+// added to the command list in render().
+
 #endif // HAS_D3D12
diff --git a/examples/quick/scenegraph/rendernode/main.qml b/examples/quick/scenegraph/rendernode/main.qml
index c647aab88d..a91656dfaa 100644
--- a/examples/quick/scenegraph/rendernode/main.qml
+++ b/examples/quick/scenegraph/rendernode/main.qml
@@ -71,9 +71,9 @@ Item {
             NumberAnimation { target: rotation; property: "angle"; to: 80; duration: 1000; easing.type: Easing.InOutCubic }
             NumberAnimation { target: rotation; property: "angle"; to: -80; duration: 1000; easing.type: Easing.InOutCubic }
             NumberAnimation { target: rotation; property: "angle"; to: 0; duration: 1000; easing.type: Easing.InOutCubic }
-            NumberAnimation { target: renderer; property: "opacity"; to: 0.5; duration: 1000; easing.type: Easing.InOutCubic }
+            NumberAnimation { target: renderer; property: "opacity"; to: 0.1; duration: 1000; easing.type: Easing.InOutCubic }
             PauseAnimation { duration: 1000 }
-            NumberAnimation { target: renderer; property: "opacity"; to: 0.8; duration: 1000; easing.type: Easing.InOutCubic }
+            NumberAnimation { target: renderer; property: "opacity"; to: 1.0; duration: 1000; easing.type: Easing.InOutCubic }
             ParallelAnimation {
                 NumberAnimation { target: scale; property: "xScale"; to: 1; duration: 1000; easing.type: Easing.InOutBack }
                 NumberAnimation { target: scale; property: "yScale"; to: 1; duration: 1000; easing.type: Easing.InOutBack }
diff --git a/examples/quick/scenegraph/rendernode/openglrenderer.cpp b/examples/quick/scenegraph/rendernode/openglrenderer.cpp
index 27712e13b2..3eff70cb42 100644
--- a/examples/quick/scenegraph/rendernode/openglrenderer.cpp
+++ b/examples/quick/scenegraph/rendernode/openglrenderer.cpp
@@ -57,9 +57,6 @@ OpenGLRenderNode::~OpenGLRenderNode()
     releaseResources();
 }
 
-// No need to reimplement changedStates() since our rendering is so simple,
-// without involving any state changes.
-
 void OpenGLRenderNode::releaseResources()
 {
     delete m_program;
@@ -84,8 +81,9 @@ void OpenGLRenderNode::init()
 
     static const char *fragmentShaderSource =
         "varying lowp vec4 col;\n"
+        "uniform lowp float opacity;\n"
         "void main() {\n"
-        "   gl_FragColor = col;\n"
+        "   gl_FragColor = col * opacity;\n"
         "}\n";
 
     m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
@@ -95,6 +93,7 @@ void OpenGLRenderNode::init()
     m_program->link();
 
     m_matrixUniform = m_program->uniformLocation("matrix");
+    m_opacityUniform = m_program->uniformLocation("opacity");
 
     const int VERTEX_SIZE = 6 * sizeof(GLfloat);
 
@@ -123,6 +122,7 @@ void OpenGLRenderNode::render(const RenderState *state)
 
     m_program->bind();
     m_program->setUniformValue(m_matrixUniform, *state->projectionMatrix() * *matrix());
+    m_program->setUniformValue(m_opacityUniform, float(inheritedOpacity()));
 
     m_vbo->bind();
 
@@ -140,7 +140,15 @@ void OpenGLRenderNode::render(const RenderState *state)
     m_program->enableAttributeArray(0);
     m_program->enableAttributeArray(1);
 
+    f->glEnable(GL_BLEND);
+    f->glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+
     f->glDrawArrays(GL_TRIANGLES, 0, 3);
 }
 
+QSGRenderNode::StateFlags OpenGLRenderNode::changedStates() const
+{
+    return BlendState;
+}
+
 #endif // QT_NO_OPENGL
diff --git a/examples/quick/scenegraph/rendernode/openglrenderer.h b/examples/quick/scenegraph/rendernode/openglrenderer.h
index 3f38faf458..28d528e617 100644
--- a/examples/quick/scenegraph/rendernode/openglrenderer.h
+++ b/examples/quick/scenegraph/rendernode/openglrenderer.h
@@ -57,6 +57,7 @@ public:
 
     void render(const RenderState *state) override;
     void releaseResources() override;
+    StateFlags changedStates() const override;
 
 private:
     void init();
@@ -64,6 +65,7 @@ private:
     QQuickItem *m_item;
     QOpenGLShaderProgram *m_program = nullptr;
     int m_matrixUniform;
+    int m_opacityUniform;
     QOpenGLBuffer *m_vbo = nullptr;
 };
 
diff --git a/examples/quick/scenegraph/rendernode/shader.hlsl b/examples/quick/scenegraph/rendernode/shader.hlsl
index 8b9b9ff9d8..f300fe7aa5 100644
--- a/examples/quick/scenegraph/rendernode/shader.hlsl
+++ b/examples/quick/scenegraph/rendernode/shader.hlsl
@@ -2,15 +2,16 @@ cbuffer ConstantBuffer : register(b0)
 {
         float4x4 modelview;
         float4x4 projection;
+        float opacity;
 };
 
 struct PSInput
 {
         float4 position : SV_POSITION;
-        float4 color : COLOR;
+        float3 color : COLOR;
 };
 
-PSInput VS_Simple(float4 position : POSITION, float4 color : COLOR)
+PSInput VS_Simple(float4 position : POSITION, float3 color : COLOR)
 {
         PSInput result;
 
@@ -23,5 +24,5 @@ PSInput VS_Simple(float4 position : POSITION, float4 color : COLOR)
 
 float4 PS_Simple(PSInput input) : SV_TARGET
 {
-        return input.color;
+        return float4(input.color, 1.0) * opacity;
 }