/****************************************************************************
**
** 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-materials.html
    \previouspage studio-3d-model.html
    \nextpage studio-3d-texture.html

    \title Materials and Shaders

    \image studio-qtquick-3d-material.png "Material attached to model in Design mode"

    Materials and shaders define how object surfaces are rendered in \QDS and
    live preview. As you change the properties of materials, new shaders are
    generated accordingly, and the property values are bound. The complexity of
    a shader depends on a combination of the properties that are set on it, and
    the context of the scene itself.

    The materials that you used in your imported scenes are imported to \QDS
    as \l{Qt Quick 3D} components. When you add a View3D component, it contains
    a DefaultMaterial component. You can use the following predefined Qt Quick
    3D components to add materials to models:

    \list
        \li Default material
        \li Principled material
        \li \l{Custom Effects and Materials}{Custom material}
        \li Texture
    \endlist

    Before a model can be rendered in a scene, it must have at least one
    material to define how the mesh is shaded. The DefaultMaterial component
    is the easiest way to define such a material. The PrincipledMaterial
    component specifies the minimum amount of properties. The CustomMaterial
    component enables you to construct your own materials.

    You can use the \l Texture component to apply textures to materials. It
    defines an image and how the image is mapped to meshes in a 3D scene. For
    more information, see \l {Textures}.

    You can modify material properties in the \uicontrol Properties view, as
    instructed in the following sections. The availability of the properties
    depends on the material type.

    \image studio-qtquick-3d-default-material.png "DefaultMaterial properties"

    To enable the material to use vertex colors from the mesh, select the
    \uicontrol {Enable vertex colors} check box. These are multiplied
    by any other colors specified for the material.

    You can animate material properties in the \uicontrol Timeline view, as
    instructed in \l {Creating Timeline Animations}.

    \section1 Blending Colors

    To determine how the colors of a model blend with the colors of the models
    behind it, set the \uicontrol {Blend mode} property. To make opaque objects
    occlude the objects behind them, select \uicontrol {SourceOver}.

    For a lighter result, select \uicontrol Screen to blend colors using an
    inverted multiply or \uicontrol ColorDodge to blend them by inverted
    division. Color dodge procudes an even lighter result than screen.

    For a darker result, select \uicontrol Multiply to blend colors using a
    multiply or \uicontrol ColorBurn to blend them by inverted division, where
    the result also is inverted. Color burn produces an even darker result than
    multiply.

    The screen and multiply modes are order-independent, so select them to
    avoid \e popping, which can happen when using semi-opaque objects and
    sorting the back and front faces or models.

    For a result with higher contrast, select \uicontrol Overlay, which is a mix
    of the multiply and screen modes.

    \section1 Lighting Materials

    To set the lighting method for generating a material, use the
    \uicontrol Lighting property. Select \uicontrol {Fragment lighting} to
    calculate diffuse and specular lighting for each rendered pixel. Some
    effects, such as Fresnel or a bump map, require fragment lighting.

    To skip lighting calculation, select \uicontrol {No lighting}. This is very
    fast and quite effective when using image maps that do not need to be shaded
    by lighting.

    To set the base color for the material, use the \uicontrol {Diffuse Color}
    property. You can either use the color picker or specify a RBG value. Set
    the diffuse color to black to create purely-specular materials, such as
    metals or mirrors. To apply a texture to a material, set it as the value of
    the \uicontrol {Diffuse map} property. Using a texture with transparency
    also applies the alpha channel as an \uicontrol {Opacity map}. You can set
    the opacity of the material independently of the model as the value of the
    \uicontrol Opacity property.

    \section1 Self-Illuminating Materials

    To set the color and amount of self-illumination for a material, use the
    \uicontrol {Emissive color} and \uicontrol {Emissive factor} properties. In
    a scene with black ambient lighting, a material with an emissive factor of 0
    is black where the light does not shine on it. Setting the emissive factor
    to 1 shows the material in its diffuse color instead.

    To use a Texture for specifying the emissive factor for different parts of
    the material, set the \uicontrol {Emissive map} property. Using a grayscale
    image does not affect the color of the result, while using a color image
    produces glowing regions with the color affected by the emissive map.

    \section1 Using Highlights and Reflections

    You can control the highlights and reflections on a material by setting the
    properties in the \uicontrol Specular group. You can use the color picker
    or set a RGB value to specify the color used to adjust specular reflections.
    Use white for no effect

    To use a color texture to modulate the amount and the color of specularity
    across the surface of a material, set the \uicontrol {Specular map}
    property. Set the \uicontrol {Specular amount} property to specify the
    strength of specularity. This property does not affect the specular
    reflection map, but it does affect the amount of reflections from a scene's
    light probe.

    \note Unless your mesh is high-resolution, you may need to use fragment
    lighting to get good specular highlights from scene lights.

    To determine how to calculate specular highlights for lights in the scene,
    set the \uicontrol {Specular model}. In addition to the default mode, you
    can use the GGX or Ward lighting model.

    To use a Texture for specular highlighting on a material, set the
    \uicontrol {Reflection map} property. When the texture is applied using
    environmental mapping (not UV mapping), the map appears to be reflecting
    from the environment as you rotate the model. Specular reflection maps are
    an easy way to add a high-quality look at a relatively low cost.

    To specify an image to use as the specular reflection map, set the
    \uicontrol {Light probe} property.

    Crisp images cause your material to look very glossy. The more you
    blur your image, the softer your material appears.

    To decrease head-on reflections (looking directly at the surface)
    while maintaining reflections seen at grazing angles, set the
    \uicontrol {Fresnel power} property. To select the angles to control,
    set the \uicontrol {Index of refraction} property.

    To control the size of the specular highlights generated from lights and the
    clarity of reflections in general, set the \uicontrol {Specular roughness}
    property. Larger values increase the roughness, while softening specular
    highlights and blurring reflections. To control the specular roughness of
    the material using a Texture, set the \uicontrol {Roughness map property}.

    \section1 Simulating Geometry Displacement

    Specify the properties in the \uicontrol {Bump/Normal} group to simulate
    fine geometry displacement across the surface of the material. Set the
    \uicontrol {Bump map} property to use a grayscale texture for the
    simulation. Brighter pixels indicate raised regions.

    To use a RGB image for simulation, set the \uicontrol {Normal map} property.
    The RGB channels indicate XYZ normal deviations.

    The amount of displacement is controlled by the \uicontrol {Bump amount}
    property.

    Bump and normal maps do not affect the silhouette of a model. To affect the
    silhouette, set the \uicontrol {Displacement map} property. It specifies a
    grayscale image used to offset the vertices of geometry across the surface
    of the material. The \uicontrol {Displacement amount} property specifies the
    offset amount.

    \section1 Specifying Material Translucency

    Set the properties in the \uicontrol Translucency group to control how much
    light can pass through the material from behind. To use a grayscale texture,
    specify it as the value of the \uicontrol {Translucency map} property.

    To specify the amount of light wrap for the translucency map, set the
    \uicontrol {Diffuse light wrap} property. A value of 0 does not wrap the
    light at all, while a value of 1 wraps the light all around the object.

    To specify the amount of falloff for the translucency based on
    the angle of the normals of the object to the light source, set
    the \uicontrol {Translucency falloff} property.

    \section1 Culling Faces

    Set the \uicontrol {Culling mode} property to determine whether the front
    and back faces of a model are rendered. Culling modes check whether the
    points in the polygon appear in clockwise or counter-clockwise order when
    projected onto the screen. If front-facing polygons have a clockwise
    winding, but the polygon projected on the screen has a counter-clockwise
    winding, the projected polygon is rotated to face away from the camera and
    is not rendered. Culling makes rendering objects quicker and more efficient
    by reducing the number of polygons to draw.

    \section1 Applying Materials to Models

    To apply materials to models, you should first delete the default material,
    and then drag-and-drop a new material from \l Library to a model component
    in \l Navigator.

    You can apply the same material to another component as well. Again,
    delete the default material first. You should then select the component and
    go to the \uicontrol Properties view. Find the \uicontrol Materials property,
    select the \inlineimage icons/plus.png
    icon, and choose the new material in the dropdown menu.
*/
