Doc: Add general guidelines for preparing 3D assets for export

These guidelines help optimize the 3D assets for importing them to
Qt Design Studio.

Fixes: QDS-1431
Change-Id: I267c3897b8da42271948d2b1e45596e3928dbf1f
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

doc/qtdesignstudio/src/qtbridge/qtbridge-overview.qdoc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the Qt Design Studio documentation.
@@ -49,17 +49,11 @@
             You can use the \QBSK export tool in Sketch to convert artwork into
             Qt Quick files that you can import to projects in \QDS.
 
-        \li \l{Exporting from Maya}
-
-            You can export 3D graphics from Maya in the FBX format.
-            The necessary plugin is usually enabled by default.
-
-        \omit
         \li \l{Exporting 3D Assets}
 
             You can import files you created using 3D graphics applications and
             stored in several widely-used formats, such as .blend, .dae, .fbx,
             .glb, .gltf, .obj, .uia, or .uip.
-        \endomit
+
     \endlist
 */

doc/qtdesignstudio/src/qtbridge/qtbridge-sketch-using.qdoc

@@ -27,7 +27,7 @@
     \contentspage {Qt Design Studio Manual}
     \previouspage qtbridge-sketch-setup.html
     \page qtbridge-sketch-using.html
-    \nextpage exporting-from-maya.html
+    \nextpage exporting-3d-assets.html
 
     \title Using \QBSK
 

doc/qtdesignstudio/src/qtquick3d-editor/exporting-3d/exporting-3d-assets.qdoc

@@ -0,0 +1,196 @@
+/****************************************************************************
+**
+** Copyright (C) 1993-2009 NVIDIA Corporation.
+** Copyright (C) 2020 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.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \contentspage {Qt Design Studio}
+    \page exporting-3d-assets.html
+    \previouspage qtbridge-sketch-using.html
+    \nextpage exporting-from-blender.html
+
+    \title Exporting 3D Assets
+
+    You can import files you created using 3D graphics applications and exported
+    to several widely-used formats, such as .blend, .dae, .fbx, .glb, .gltf,
+    .obj, .uia, or .uip. For a list of formats supported by each \l{Qt Quick 3D}
+    version, see the module documentation.
+
+    Depending on the 3D graphics tool, you might need to install export plugins
+    to be able to export files to a particular format.
+
+    To get the best results when exporting 3D assets and importing them to
+    \QDS, follow the general guidelines in the following sections. For more
+    information about using the export plugins for a particular tool, see
+    \l{Exporting from Different Tools}.
+
+    \section1 Geometry
+
+    \QDS supports geometry exported as triangles, quads, and pentagons. For
+    basic geometry, you mostly need to pay attention to pivot points and
+    transformation.
+
+    \section2 Pivot Points
+
+    In \QDS, there is only one pivot per component. It is used as the origin
+    for scaling and rotation. Adjust the position of a 3D model's pivot as
+    needed.
+
+    However, extreme edits to pivots in 3D modeling tools can cause problems
+    when importing to \QDS, especially if animated. This difference is often
+    manifested as a difference in the position or orientation of a component.
+    You can prevent these kinds of problems by only making simple edits to
+    your pivot points. Keep your pivot points to the default (world) alignment,
+    don't scale them, and make sure that if you have multiple pivots (Maya)
+    that they are all at the same location in space.
+
+    \section2 Transformation
+
+    You can import full 3D transform information including position, rotation,
+    scale, and pivot. \QDS can import left and right-handed coordinate systems,
+    y-up or z-up, and rotations applied in any order. The principal limitation
+    in this area are pivot points. As discussed above, only simple edits to
+    pivot points are supported.
+
+    Most 3D graphics tools enable you to apply transformation to components and
+    vertices. We highly recommend doing so before importing mesh data into \QDS.
+    This ensures that the mesh coming into \QDS has clean transform data and no
+    arbitrary transform values which can be confusing or an impediment to your
+    work.
+
+    \note After applying transformations, you may have to reposition the pivot
+    point in some 3D graphics tools.
+
+    \section1 Animations
+
+    Animations are supported on any imported property. Position, rotation,
+    scale, and pivot can all be animated. For example, a hierarchy of items,
+    rotated simultaneously on arbitrary axes in arbitrary axis order can be
+    imported. \QDS also supports importing bezier tangent value tweaked into
+    animations.
+
+    \section2 Time-based Animations
+
+    In many 3D modeling tools, when you create keyframes you associate them with
+    frame numbers. This is great in the film industry where frame rates are
+    constant, but poses problems in applications where the frame rate may or
+    may not be rock solid. If you were to specify that the logo animation will
+    play for 180 frames, it might play for 3 seconds at 60 FPS, but if the speed
+    drops to 30 fps, the animation will also get much slower.
+
+    Luckily, accounting for this is relatively simple. Many 3D modeling tools
+    default to a setting of 24 frames per second, so your keyframes will
+    be translated at that ratio. If you want a keyframe at one second, put
+    it on frame 24. For two seconds, use frame 48, and so on.
+
+    Usually, configurable frame rates are offered, and the frame rate setting
+    should be respected upon import.
+
+    Some tools, such as Maya, start at frame 1, by default. If you have a
+    keyframe at frame 1, the time for that keyframe will be 1/24, or 0.041
+    seconds. Edit your Maya animation settings to start your animations at
+    frame 0, or 0/24 = 0 seconds.
+
+    In \QDS, you can specify the duration of the animation in addition to its
+    start and end frame.
+
+    \section2 Deform Animations
+
+    \e {Deform animations}, such as lattice and bend, are not supported by \QDS.
+    However, you can work around this limitation by converting deform animations
+    into \e {blend shape} animations that are supported in FBX format. Before
+    exporting the animations, you need to bake the actions in them into key
+    frames.
+
+    \section2 Baking Actions for Animations
+
+    You need to bake actions to export animations that are using custom curves
+    or object constraints to control the animation.
+
+    \e Actions are data-blocks containing animation data. If you are exporting
+    animations, you need to bake actions.
+
+    \section2 Animation Systems
+
+    3D modeling tools offer highly complex and specialized animation systems.
+    We recommend using the \QDS \uicontrol Timeline view whenever practical.
+    This helps keep mesh information on import clean and reduces conflicts
+    between imported mesh animation and \QDS's animation.
+
+    The animation system in \QDS is a full implementation of bezier
+    keys, and the full complement of bezier animation that you can create
+    with 3D modeling tools and export are represented in \QDS. The more
+    extreme differences between the various animation systems are mitigated
+    by the limitations imposed by the supported formats.
+
+    \section1 Materials and Textures
+
+    Create and assign material slots in the 3D graphics tool before you export
+    3D graphics. If you add several material slots, the first one is assigned
+    to the object. Only material slots that have a material and that are
+    assigned to a mesh on the exported object are imported into \QDS.
+
+    If no material slots are assigned to an object, a default material is
+    attached to the component that is created when you import the assets to
+    \QDS.
+
+    UV-unwrapping your model will create a UV layout. Without a UV layout, you
+    will not be able to render any textures on your model in \QDS.
+
+    There are many different ways and techniques to unwrap 3D meshes, depending
+    on the 3D graphics tool.
+
+    \section1 Lights
+
+    Lights are imported to \QDS. Position, rotation, scale, brightness,
+    light color, and the cast shadows property values are preserved.
+
+    If the light type is not supported by Qt Quick 3D, it is converted into
+    one of the supported types.
+
+    \section1 Cameras
+
+    Perspective and orthographic cameras are imported to \QDS. Position,
+    rotation, and scale property values, as well as start and end clipping
+    values are preserved. For perspective cameras, field of view values
+    are also preserved.
+
+    \section1 Node Hierarchy
+
+    \QDS supports importing hierarchical information. Hierarchies of arbitrary
+    depth are supported, including grouped nodes. Hierarchical transforms are
+    applied as expected.
+
+    \section1 Exporting from Different Tools
+
+    The following sections provide additional information about exporting
+    3D assets from a particular tool:
+
+    \list
+        \li \l{Exporting from Blender}{Blender}
+        \li \l{Exporting from Maya}{Maya}
+    \endlist
+*/