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/****************************************************************************
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** Copyright (C) 2019 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
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/*!
\page studio-3d-camera.html
\previouspage studio-3d-lights.html
\nextpage studio-3d-scene-environment.html
\title Using Scene Camera
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 3D view.
You can use the following 3D QML types 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 types 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.
\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.
*/
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