Scene3D: only show SGNode once Qt3D has first rendered into it

Avoids seeing garbage for the first frame (with planets-qml)

Change-Id: I3445ce47f27bb921c15861e580a8cc6c7d8cc645
Reviewed-by: Mike Krus <mike.krus@kdab.com>

7 files changed, 27 insertions, 1 deletions

diff --git a/src/quick3d/imports/scene3d/scene3drenderer.cpp b/src/quick3d/imports/scene3d/scene3drenderer.cpp
index bc4dbd362..1e375ccbb 100644
--- a/src/quick3d/imports/scene3d/scene3drenderer.cpp
+++ b/src/quick3d/imports/scene3d/scene3drenderer.cpp
@@ -419,6 +419,10 @@ void Scene3DRenderer::render()
 
         // Restore QtQuick FBO
         QOpenGLFramebufferObject::bindDefault();
+
+        // Only show the node once Qt3D has rendered to it
+        // Avoids showing garbage on the first frame
+        m_node->show();
     }
 
     // Reset the state used by the Qt Quick scenegraph to avoid any
diff --git a/src/quick3d/imports/scene3d/scene3dsgmaterial.cpp b/src/quick3d/imports/scene3d/scene3dsgmaterial.cpp
index 1b8b08a4e..80a1c2c9c 100644
--- a/src/quick3d/imports/scene3d/scene3dsgmaterial.cpp
+++ b/src/quick3d/imports/scene3d/scene3dsgmaterial.cpp
@@ -60,6 +60,7 @@ namespace Qt3DRender {
 Scene3DSGMaterial::Scene3DSGMaterial()
     : QSGMaterial()
     , m_texture(nullptr)
+    , m_visible(false)
 {
 }
 
diff --git a/src/quick3d/imports/scene3d/scene3dsgmaterial_p.h b/src/quick3d/imports/scene3d/scene3dsgmaterial_p.h
index c096f2a74..59724782b 100644
--- a/src/quick3d/imports/scene3d/scene3dsgmaterial_p.h
+++ b/src/quick3d/imports/scene3d/scene3dsgmaterial_p.h
@@ -75,8 +75,12 @@ public:
     QSGMaterialType *type() const final { return &Scene3DSGMaterialShader::type; }
     QSGMaterialShader *createShader() const final { return new Scene3DSGMaterialShader(); }
 
+    void show() { m_visible = true; }
+    bool visible() const { return m_visible; }
+
 private:
     QSGTexture *m_texture;
+    bool m_visible;
 };
 
 } // namespace Qt3DRender
diff --git a/src/quick3d/imports/scene3d/scene3dsgmaterialshader.cpp b/src/quick3d/imports/scene3d/scene3dsgmaterialshader.cpp
index d25c6a7f7..55538ad1f 100644
--- a/src/quick3d/imports/scene3d/scene3dsgmaterialshader.cpp
+++ b/src/quick3d/imports/scene3d/scene3dsgmaterialshader.cpp
@@ -118,21 +118,25 @@ const char *Scene3DSGMaterialShader::fragmentShader() const
     if (ctx->format().version() >= qMakePair(3, 2) && ctx->format().profile() == QSurfaceFormat::CoreProfile) {
         return ""
                "#version 150 core                                   \n"
+               "uniform bool visible;                               \n"
                "uniform sampler2D source;                           \n"
                "uniform float qt_Opacity;                           \n"
                "in vec2 qt_TexCoord;                                \n"
                "out vec4 fragColor;                                 \n"
                "void main() {                                       \n"
-               "   vec4 p = texture(source, qt_TexCoord);         \n"
+               "   if (!visible) discard;                           \n"
+               "   vec4 p = texture(source, qt_TexCoord);           \n"
                "   float a = qt_Opacity * p.a;                      \n"
                "   fragColor = vec4(p.rgb * a, a);                  \n"
                "}";
     } else {
         return ""
+               "uniform bool visible;                                   \n"
                "uniform highp sampler2D source;                         \n"
                "uniform highp float qt_Opacity;                         \n"
                "varying highp vec2 qt_TexCoord;                         \n"
                "void main() {                                           \n"
+               "   if (!visible) discard;                               \n"
                "   highp vec4 p = texture2D(source, qt_TexCoord);       \n"
                "   highp float a = qt_Opacity * p.a;                    \n"
                "   gl_FragColor = vec4(p.rgb * a, a);                   \n"
@@ -144,6 +148,7 @@ void Scene3DSGMaterialShader::initialize()
 {
     m_matrixId = program()->uniformLocation("qt_Matrix");
     m_opacityId = program()->uniformLocation("qt_Opacity");
+    m_visibleId = program()->uniformLocation("visible");
 }
 
 void Scene3DSGMaterialShader::updateState(const RenderState &state, QSGMaterial *newEffect, QSGMaterial *oldEffect)
@@ -172,6 +177,9 @@ void Scene3DSGMaterialShader::updateState(const RenderState &state, QSGMaterial
             t->updateBindOptions();
     }
 
+    if (oldTx == nullptr || oldTx->visible() != tx->visible())
+        program()->setUniformValue(m_visibleId, tx->visible());
+
     if (state.isMatrixDirty())
         program()->setUniformValue(m_matrixId, state.combinedMatrix());
 
diff --git a/src/quick3d/imports/scene3d/scene3dsgmaterialshader_p.h b/src/quick3d/imports/scene3d/scene3dsgmaterialshader_p.h
index c372a1170..60edf6d45 100644
--- a/src/quick3d/imports/scene3d/scene3dsgmaterialshader_p.h
+++ b/src/quick3d/imports/scene3d/scene3dsgmaterialshader_p.h
@@ -74,6 +74,7 @@ protected:
 private:
     int m_matrixId;
     int m_opacityId;
+    int m_visibleId;
 };
 
 } // namespace Qt3DRender
diff --git a/src/quick3d/imports/scene3d/scene3dsgnode.cpp b/src/quick3d/imports/scene3d/scene3dsgnode.cpp
index c38e9ffeb..630cf49a9 100644
--- a/src/quick3d/imports/scene3d/scene3dsgnode.cpp
+++ b/src/quick3d/imports/scene3d/scene3dsgnode.cpp
@@ -84,6 +84,12 @@ void Scene3DSGNode::setRect(const QRectF &rect, const QRectF textureRect)
     }
 }
 
+void Scene3DSGNode::show()
+{
+    m_material.show();
+    m_opaqueMaterial.show();
+}
+
 } // namespace Qt3DRender
 
 QT_END_NAMESPACE
diff --git a/src/quick3d/imports/scene3d/scene3dsgnode_p.h b/src/quick3d/imports/scene3d/scene3dsgnode_p.h
index 388c8a605..a7873bdb8 100644
--- a/src/quick3d/imports/scene3d/scene3dsgnode_p.h
+++ b/src/quick3d/imports/scene3d/scene3dsgnode_p.h
@@ -78,6 +78,8 @@ public:
     void setRect(const QRectF &rect, const QRectF textureRect = QRectF(0.0f, 1.0f, 1.0f, -1.0f));
     QRectF rect() const Q_DECL_NOTHROW { return m_rect; }
 
+    void show();
+
 private:
     Scene3DSGMaterial m_material;
     Scene3DSGMaterial m_opaqueMaterial;