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/****************************************************************************
**
** Copyright (C) 2020 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Design Studio documentation.
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
**
****************************************************************************/
/*!
\page studio-optimized-3d-scenes.html
\previouspage qtquick-optimizing-designs.html
\if defined(qtdesignstudio)
\nextpage studio-implementing-applications.html
\else
\nextpage qtquick-iso-icon-browser.html
\endif
\title Creating Optimized 3D Scenes
In \QC, you can use various means to create a 3D scene. Your choice of
strategy should always depend on the target platform of your scene.
The way the content of your scene is authored can have dramatic effects on
the runtime performance of your UI. The Optimal 3D Scene described
below illustrates four different ways to create a scene. Also see guidelines
for \l{Optimizing your 3D Scene}{optimizing the graphics performance of your 3D scene}
and \l{Best Practices for 3D Scenes Based on Use Cases}.
\section1 The Optimal 3D Scene Example
\if defined(qtdesignstudio)
The \l {Optimal 3D Scene}
\else
The Optimal 3D Scene
\endif
example features four versions of the same kitchen
scene that have been created using different strategies: High, Low, Combined,
and Vertex Color. The High Scene includes a significantly higher number of
objects compared to the other versions of the scene. The Low, Combined and
Vertex scenes include less objects since they have been optimized by, for
example, combining geometry and baking materials into textures. The
following image displays the components in each scene in \l Navigator to
illustrate the structural differences between the scenes.
\image studio-kitchen-navigators.png "Navigators for the four scenes in the Optimal 3D Scene."
\section2 The High Scene
\image studio-kitchen-high.png "The High Scene in the Optimal 3D Scene"
The High scene (1) includes a total of 27 objects. The scene is otherwise
similar to the Low scene, but has more details and animated components, such
as cabinet doors that can be opened and a latch for the oven.
\section2 The Low Scene
\image studio-kitchen-low.png "The Low Scene in the Optimal 3D Scene"
The Low scene (2) includes a total of 12 objects. Each model, for example
cabinets, lamps, plates, and the sink, are separate meshes.
\section2 The Combined Scene
\image studio-kitchen-combined.png "The Combined Scene in the Optimal 3D Scene"
The Combined scene (3) has all the meshes combined into a single object. All
materials are baked into one single texture.
\section2 The Vertex Color Scene
\image studio-kitchen-vertex.png "The Vertex Color Scene in the Optimal 3D Scene"
The Vertex Color scene (4) has all the meshes combined into a single object,
and colors for the mesh are provided from .mesh file's vertex data, which
includes one material and no textures.
\section1 Optimizing Your 3D Scene
To optimize the graphics performance of your 3D scene, you should first
consider whether you need to animate the 3D objects, lights, camera, or
other components in your scene. If not, simplify the scene structure by, for
example, combining geometries and baking materials into textures. Ideally,
pre-render your 3D image into a 2D image. You should not waste resources
by rendering static 3D objects. You should also check if your scene has
multiple instances of the same mesh. If so, import only one instance of the
mesh, duplicate it in the scene, and use the same material for each
duplicate.
See also the following guidelines related to scene graph, asset complexity,
CPU specific optimization, and model geometry.
\section2 Scene Graph
The scene graph is the hierarchy of nodes that describe the scene to be
rendered.
In \QC, the scene graph is represented by the tree-like view in
\uicontrol Navigator. You can also view the hierarchy of nodes in the
\l {Text Editor} view. By minimizing the size of the scene graph,
you can minimize the effort needed when running the scene. In terms of
optimization, you should avoid unnecessary groups and complex hierarchy when
possible. Deep hierarchies with complex parenting increase the performance
cost.
\section2 Asset Complexity
The performance of your UI or scene may sometimes be bottlenecked at render
time. Avoid this by simplifying your assets.
For 3D models, you should try to use the minimum number of triangles or
vertices to achieve the desired result. Also note that smaller images
require less memory and render faster.
\section2 Optimizing CPU Performance
Rendering objects requires plenty of processing work from the CPU.
Processing each component consumes resources, so reducing the visible object
count reduces the amount of work required from the CPU.
To reduce the visible object count:
\list
\li Combine objects that are positioned closely and share a texture.
\note Combining objects that do not share a texture does not increase
the CPU performance while running the scene.
\li Use fewer materials by combining separate textures into a single
texture atlas (like in the Merged scene in the
Kitchen Scene Example).
\li Minimize the number of factors that cause objects to be rendered
multiple times, for example reflections and shadows.
\endlist
\section2 Optimizing Model Geometry
To optimize the geometry of a model:
\list
\li Minimize the number of triangles used in the model.
\li Minimize the number of UV mapping seams and hard edges created with
doubled-up vertices.
\endlist
\section1 Best Practices for 3D Scenes Based on Use Cases
The following table summarizes best practices related to optimizing 3D
scenes in the form of use cases.
\table
\header
\li How to...
\li Solution
\row
\li Get best performance from the 3D scene.
\li If no animation is required, pre-render your 3D scene into a 2D
image.
\row
\li Include animation for some of the objects in the scene
(for example, to open doors).
\li Merge all objects that are static, and export only one of
each animated component (for example, each door type).
\row
\li Get best performance with animated camera.
\li While using a 2D image is not an option in this case, you should
combine all geometry and bake lighting and materials into a single
material.
\row
\li Get best performance with animated light.
\li While using a 2D image is not an option in this case, you should
combine all geometry and bake all materials into a single
material.
\row
\li Get best performance in a 3D scene where all meshes are
separated.
\li Use the same material for each instance of the same mesh.
\row
\li Disable rendering for one of the meshes during runtime.
\li Keep that particular mesh separate but merge the rest of the
components.
\row
\li Use baked textures with low memory.
\li Bake mesh colors into vertex colors (see the Vertex Color Scene
in the example project).
\endtable
*/
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