Introduce QGeometryRendererPrivate::sortIndex

Lets user override the sorting order of entities.

Change-Id: Iab7fd0d705f7ddcb424a59f86f8c2c28059813d1
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
(cherry picked from commit c6aec09f4f6030fa11b9ba911e4c0df2fe7485b2)

6 files changed, 40 insertions, 1 deletions

diff --git a/src/plugins/renderers/opengl/renderer/renderview.cpp b/src/plugins/renderers/opengl/renderer/renderview.cpp
index 59b323398..8c2d5a39d 100644
--- a/src/plugins/renderers/opengl/renderer/renderview.cpp
+++ b/src/plugins/renderers/opengl/renderer/renderview.cpp
@@ -839,6 +839,10 @@ void RenderView::updateRenderCommand(const EntityRenderCommandDataSubView &subVi
             // view vector. This gives a depth value suitable as the key
             // for BackToFront sorting.
             command.m_depth = Vector3D::dotProduct(entity->worldBoundingVolume()->center() - m_eyePos, m_eyeViewDir);
+
+            auto geometryRenderer = m_manager->geometryRendererManager()->data(command.m_geometryRenderer);
+            if (geometryRenderer && !qFuzzyCompare(geometryRenderer->sortIndex(), -1.f))
+                command.m_depth = geometryRenderer->sortIndex();
         } else { // Compute
             // Note: if frameCount has reached 0 in the previous frame, isEnabled
             // would be false
diff --git a/src/plugins/renderers/rhi/renderer/renderview.cpp b/src/plugins/renderers/rhi/renderer/renderview.cpp
index 54295ef5f..344dc3a3b 100644
--- a/src/plugins/renderers/rhi/renderer/renderview.cpp
+++ b/src/plugins/renderers/rhi/renderer/renderview.cpp
@@ -826,6 +826,10 @@ void RenderView::updateRenderCommand(EntityRenderCommandData *renderCommandData,
             command.m_depth = Vector3D::dotProduct(
                     entity->worldBoundingVolume()->center() - m_data.m_eyePos, m_data.m_eyeViewDir);
 
+            auto geometryRenderer = m_manager->geometryRendererManager()->data(command.m_geometryRenderer);
+            if (geometryRenderer && !qFuzzyCompare(geometryRenderer->sortIndex(), -1.f))
+                command.m_depth = geometryRenderer->sortIndex();
+
             environmentLight = m_environmentLight;
             lightSources = m_lightSources;
 
diff --git a/src/render/geometry/geometryrenderer.cpp b/src/render/geometry/geometryrenderer.cpp
index 881c0f66b..ff7ed308f 100644
--- a/src/render/geometry/geometryrenderer.cpp
+++ b/src/render/geometry/geometryrenderer.cpp
@@ -71,6 +71,7 @@ GeometryRenderer::GeometryRenderer()
     , m_primitiveType(QGeometryRenderer::Triangles)
     , m_dirty(false)
     , m_manager(nullptr)
+    , m_sortIndex(-1.f)
 {
 }
 
@@ -96,6 +97,7 @@ void GeometryRenderer::cleanup()
     m_geometryFactory.reset();
     qDeleteAll(m_triangleVolumes);
     m_triangleVolumes.clear();
+    m_sortIndex = -1.f;
 }
 
 void GeometryRenderer::setManager(GeometryRendererManager *manager)
@@ -151,6 +153,9 @@ void GeometryRenderer::syncFromFrontEnd(const QNode *frontEnd, bool firstTime)
         }
     }
 
+    const auto dnode = static_cast<const QGeometryRendererPrivate*>(QGeometryRendererPrivate::get(node));
+    m_sortIndex = dnode->m_sortIndex;
+
     markDirty(AbstractRenderer::GeometryDirty);
 }
 
diff --git a/src/render/geometry/geometryrenderer_p.h b/src/render/geometry/geometryrenderer_p.h
index a38233d6c..411845819 100644
--- a/src/render/geometry/geometryrenderer_p.h
+++ b/src/render/geometry/geometryrenderer_p.h
@@ -104,6 +104,8 @@ public:
     // Pick volumes job
     QVector<RayCasting::QBoundingVolume *> triangleData() const;
 
+    float sortIndex() const { return m_sortIndex; }
+
 private:
     Qt3DCore::QNodeId m_geometryId;
     int m_instanceCount;
@@ -120,6 +122,7 @@ private:
     QGeometryFactoryPtr m_geometryFactory;
     GeometryRendererManager *m_manager;
     QVector<RayCasting::QBoundingVolume *> m_triangleVolumes;
+    float m_sortIndex;
 };
 
 class GeometryRendererFunctor : public Qt3DCore::QBackendNodeMapper
diff --git a/src/render/geometry/qgeometryrenderer.cpp b/src/render/geometry/qgeometryrenderer.cpp
index 8720a5c00..7abbe8db8 100644
--- a/src/render/geometry/qgeometryrenderer.cpp
+++ b/src/render/geometry/qgeometryrenderer.cpp
@@ -48,6 +48,28 @@ using namespace Qt3DCore;
 
 namespace Qt3DRender {
 
+/*
+    \internal
+
+    sortIndex property: overrides the sorting index when depth sorting is enabled.
+
+    If depth sorting is enabled on the frame graph, the renderer will sort
+    objects based on how far the center of the bounding volume is from
+    the camera and render objects from the furthest to the closest.
+
+    This property can be used to override the depth index and precisely
+    control the order in which objects are rendered. This is useful when
+    all objects are at the same physical distance from the camera.
+
+    The actual values are not significant, only that they define an order
+    to sort the objects. These are sorted such as the object with the
+    smallest value is drawn first, then the second smallest, and so on.
+
+    \note Setting this to -1.f will disable the explicit sorting for this
+    entity and revert to using the distance from the center of the bounding
+    volume.
+*/
+
 QGeometryRendererPrivate::QGeometryRendererPrivate()
     : QComponentPrivate()
     , m_instanceCount(1)
@@ -61,6 +83,7 @@ QGeometryRendererPrivate::QGeometryRendererPrivate()
     , m_primitiveRestart(false)
     , m_geometry(nullptr)
     , m_primitiveType(QGeometryRenderer::Triangles)
+    , m_sortIndex(-1.f)
 {
 }
 
@@ -194,7 +217,6 @@ QGeometryRendererPrivate::~QGeometryRendererPrivate()
     \sa Qt3DRender::QGeometryRenderer::PrimitiveType
  */
 
-
 /*!
     Constructs a new QGeometryRenderer with \a parent.
  */
diff --git a/src/render/geometry/qgeometryrenderer_p.h b/src/render/geometry/qgeometryrenderer_p.h
index 32ca334e3..323ab786c 100644
--- a/src/render/geometry/qgeometryrenderer_p.h
+++ b/src/render/geometry/qgeometryrenderer_p.h
@@ -82,6 +82,7 @@ public:
     QGeometry *m_geometry;
     QGeometryRenderer::PrimitiveType m_primitiveType;
     QGeometryFactoryPtr m_geometryFactory;
+    float m_sortIndex;
 };
 
 struct QGeometryRendererData