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/****************************************************************************
**
** Copyright (C) 2019 Luxoft Sweden AB
** Copyright (C) 2018 Pelagicore AG
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Neptune 3 IVI UI.
**
** $QT_BEGIN_LICENSE:FDL-QTAS$
** Commercial License Usage
** Licensees holding valid commercial Qt Automotive Suite 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.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page neptune3ui-3d-integration.html
\title Neptune 3 UI - 3D Integration
\brief The 3D Integration in Neptune 3 UI
In Neptune 3, a built-in application called "com.luxoft.vehicle" is included
as the vehicle settings application and contains a car 3D scene on top of
its content. The 3D scene is renderred by \l{Qt 3D} that provides
functionality for near-realtime simulation systems with support for 2D and 3D
rendering in both Qt C++ and Qt Quick applications.
\section1 3D Modeling
A general question about a 3D framework is to provide ways to draw 3D shapes,
move them around and move the camera. This is, of course, a sensible baseline,
and additional wishes typically include the following:
\list
\li Mesh: a mesh is a collection of vertices and edges which are probably triangulated
and describes the shape of an object in 3D space
\li Material: a material is a set of coefficients
that define how the lighting should be applied to the model and interacts with the
surface
\li Shader: a shader is a programmable shading that is used to do
shading, as the production of appropriate levels of color within an image, as well
as to produce special effects or do video post-processing
\li Texture: Textures are typically used for images to decorate 3D models, but for other
purposes it can also be used to store many different kinds of data
\li Camera: The first thing to do in the projection of the screen of a scene is to convert 3D
coordinates into 2D coordinates. To specify the projection, the points in the 3D
scene is used on a virtual screen space. The parameters of a projection will not be
entered directly, instead, virtual camera is configured and placed.
\li Animation: Movements of objects are important and can be accomplished by altering the
object positions
\endlist
\section1 Qt 3D
The \l{Qt 3D} provides some functionalities for modern 3D rendering backed by
the performance of OpenGL across the platforms supported by Qt. Qt3D allows developers
not only to visualize 3D contents but also to totally customize and control the
appearance of each object by using built-in materials or by providing custom GLSL
shaders. These controls are also accessible through QML that literally extend the ability
to create a 3D user interface. Integration of 2D and 3D contents is enabled by the
Scene3D component through QML. Qt3D is an Entity Component System (ECS), an architectural
pattern used mostly in game development.
An application that uses the ECS pattern involves the following:
\list
\li Entity: A container for any components that can be added, usually hierarchical.
An entity represents an object of components but by itself is devoid of any
specific behavior or characteristics. (An entity can also have sub-Entities)
\li Component: Set of objects through which behaviors and data can be added
to an entity
\endlist
\image 3d-integration-ecs.jpg
An Entity with a Component attached will tell the system that it needs to be rendered
and how to render it. The components of each entity could be the material, mesh or
transformation. These components should be defined as the components of particular
entity with a given identity of each component. A material component could have a
material effect that contains the rendering technique. In addition, within the
rendering technique, the shader programs can also be specified. These shader programs
can be an external shader files or directly written in QML. The 3D model might has
textures, and the connection between the 3D model and the textures can be binded
by using the shader and include the material component which has these material
effect to the same entity as the mesh component.
\section1 3D Integration in Neptune 3 UI
The current structure of the vehicle application:
\image 3d-integration-vehicle-app.jpg
As shown in the above image, each part of the vehicle has its own entity that contains
all the necessary parts, such as Mesh, Transform and Material. Those entities are tailored
to the root entity of the whole Scene 3D.
Neptune 3 UI has an own custom physical based material with Cook Torrance GGX distribution
since Qt3D does not provide any for OpenGL ES 2.0. It is required, because it has microfacet
theory based lightning, which adds more realistic lightning to the car. Car is mostly covered
with a color, so its easy to integrate lightning calculations. Also most of models today are
modeled with PBR (Metal Roughness) materials in mind, which will make easier model import.
Animations in vehicle applications are made mostly with matrices transformations. For example
door animation is: transform door to another origin, rotate it, transform back. So the door
will not rotate around own axis.
*/
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