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The default compositing mode is FBO.
One of the problematic aspects of Scene3D is its round trip
through a FBO, which is moderately expensive on low-end hardware,
although it makes it a fully fledged Qt Quick 2 item. If one
wants MSAA then things are even worse, as an intermediate MS'ed
FBO is needed, then resolving into the final one, whose color
texture is then sampled.
However, there's a significant use case for which these FBOs
can be avoided, and that's the case of a 3D scene "below" other
QQ2 content. In this setup, Qt3D can simply render to the
screen, driven by QQ2; then QQ2 can draw on top.
(It's the typical "underlay" scenario.) This can be enabled by setting
the compositing mode to Underlay
[ChangeLog] Scene3D add compositingMode property. Allows underlay rendering.
Task-number: QTBUG-74977
Change-Id: I1ec5f5d60eab45835dbdb2596a7bf1b2ac3624e0
Reviewed-by: Mike Krus <mike.krus@kdab.com>
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