// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \example customeffect
    \ingroup quick3d-examples
    \title Qt Quick 3D - Custom Effect Example
    \examplecategory {3D}
    \brief Demonstrates writing custom post-processing effects.
    \image customeffect-example.jpg
           {Warped scene with pink Qt logo and checkered floor showing
           custom post-processing effects}

    The example implements its own custom post-processing effects, which are then applied on
    the scene via \l SceneEnvironment::effects. It demonstrates both the simplest type of
    effects that only have a fragment shader, and also the more advanced case with both a
    vertex and fragment shader present, with data passed between the two.

    The simple effect is using only a single fragment shader, and adding a texture input from
    an image file:

    \snippet customeffect/main.qml eff1

    This effect uses a very simple fragment shader, just taking the input texture containing
    the scene, and multiplying it with the image texture:

    \quotefile customeffect/effect.frag

    The shader snippets in the \c{.vert} and \c{.frag} files are written using the
    built-in keywords as described in the \l Effect documentation. Custom properties with
    basic types, as well as properties with the \l TextureInput type are automatically
    exposed to the shaders as uniforms and samplers.


    The second effect is more complex. It specifies both a vertex and a fragment shader, as
    well as two properties: \c uRed and \c uGreen, with an animation on \c uRed:

    \snippet customeffect/main.qml eff2

    The fragment shader for this effect creates a distortion by modifying the sampling
    coordinates. The calculation uses \c center_vec, a VARYING set by the vertex shader
    that holds the aspect-ratio-corrected vector from the screen center to the current
    fragment. Finally, the shader adjusts the color using the \c uRed and \c uGreen
    uniforms. Note that these uniforms do not have to be declared in the shader:

    \quotefile customeffect/effect2.frag
*/
