/****************************************************************************
**
** Copyright (C) 2021 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt Design Studio.
**
** $QT_BEGIN_LICENSE:FDL$
** 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.
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \page studio-3d-camera.html
    \previouspage studio-3d-lights.html
    \nextpage studio-3d-scene-environment.html

    \title Cameras

    A camera is always necessary to view the content of a 3D scene. A camera
    defines how to project the content of a 3D scene into a 2D coordinate space,
    which can then be used on a 2D surface. When a camera is present in the
    scene, it can be used to direct what is displayed in a \l {3D Views}
    {3D view}.

     \image studio-qtquick-3d-components.png "Qt Quick 3D components in Library"

    You can add a camera to your scene by dragging-and-dropping one from
    \l Library > \uicontrol Components > \uicontrol {Qt Quick 3D} > \uicontrol
    {Qt Quick 3D} to \l {3D Editor} or to a 3D view in \l Navigator.
    If the cameras are not displayed in \uicontrol Library, you should add the
    \uicontrol QtQuick3D module to your project, as described in
    \l {Adding and Removing Modules}.

    You can use the following components in your scenes to determine camera
    projection:

    \list
        \li \l{PerspectiveCamera}{Camera Perspective} - is the standard camera
            type, which uses field of view and near and far clip planes to
            specify the projection.
        \li \l{OrthographicCamera}{Camera Orthographic} - renders all contents
            with no perspective. It is ideal for rendering 2D elements, because
            your images are guaranteed to be the right size on the screen, and
            you can use the z position of components to bring them closer to or
            take them farther from the camera (\e z-sorting) with no
            foreshortening artifacts.
        \li \l{FrustumCamera}{Camera Frustum} - enables finer grain control of
            how the frustum is defined, by setting the number of degrees between
            the top and bottom or left and right edges of the camera frustum.
            This is useful when creating asymmetrical frustums.
        \li \l{CustomCamera}{Camera Custom} - provides  full control over how
            the projection matrix is created.
    \endlist

    You can position the camera in the scene and set the direction it is facing.
    The default direction of the camera is such that the forward vector is
    looking up the +z axis, and the up direction vector is up the +y axis. You
    can apply transforms to the camera and its parent components to define
    exactly where your camera is located and in which direction it is facing.

    The second part of determining the projection of the camera is defining the
    field of view (\e frustum) of the camera that defines which parts of the
    scene are visible, as well as how they are visible.

    You can edit the camera properties in the \uicontrol Properties view.

   \image studio-qtquick-camera-properties "Properties view for Perspective Camera"

    \section1 Setting Camera Field of View

    The camera frustum can be obtained by taking a frustum (that is, a
    truncation with parallel planes) of the cone of vision that a camera or eye
    would have to the rectangular viewports typically used in computer graphics.
    The shape of the cone depends on the camera lens that is being simulated.
    Typically, it is a rectangular pyramid with the top cut off.

    The planes that cut the frustum perpendicular to the viewing direction are
    called the \e {near plane} and the \e {far plane}. Components in front of
    the near plane or behind the far plane are not drawn.

    The \uicontrol {Clip near} and \uicontrol {Clip far} properties determine
    the position of the near plane and the far plane. We recommend that
    you place the near and far planes as close to each other as possible to
    optimize depth accuracy. Components are clipped at pixel level instead of
    element level. This means that a model crossing a plane may be only
    partially rendered.

    The \uicontrol {Field of view} (FOV) property specifies the number of
    degrees between the edges of the camera frustum. The larger the value,
    the stronger the sense of 3D in your scene. By default, the
    \uicontrol {FOV orientation} property is set to use the vertical FOV.
    This value is the number of degrees between the top and bottom edges
    of the camera frustum.

    The horizontal FOV determines the number of degrees between the left and
    right edges of the camera frustum. It is automatically calculated based on
    the aspect ratio of the scene when the FOV orientation is set to vertical.
    You can set the orientation to horizontal to translate FOV values from
    graphics tools such as Maya and Blender, which use horizontal FOV by
    default.

    The default values are intended to cause anything within the view
    of the camera to be rendered. Aside from special clipping effects, you
    may need to adjust these values to more closely contain your content for
    better results with ambient occlusion or with effects that use the depth
    buffer of the camera, such as the \e {depth of field} effect.

    \note Orthographic cameras don't have the FOV property.
*/
