qtquick3d-tool-balsam.qdoc

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// Copyright (C) 2019 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
\page qtquick3d-tool-balsam.html
\title Balsam Asset Import Tool
\brief Tool for importing assets for use with Qt Quick 3D
 
The Balsam tool is an application that is part of Qt Quick 3D's
asset conditioning pipeline. The purpose is to take assets created in digital
content creation tools like
\l{https://www.autodesk.com/products/maya/overview}{Maya},
\l{https://www.autodesk.com/products/3ds-max/overview}{3ds Max}, or
\l{https://www.blender.org/}{Blender} and convert them into an efficient runtime
format for use with Qt Quick 3D. It is not possible, nor does it make sense to
reference the interchange formats directly in applications because a large amount
of resources are needed to parse and condition the content of the asset before it
is usable for realtime rendering. Instead the interchange formats can be
converted via the Balsam tool into QML Components and resources like geometry and
textures.
 
\section1 Balsam Command Line Tool
 
To run Balsam through the command line, call the \c balsam executable like
this:
 
\code
balsam [options] sourceFilename
\endcode
 
To convert a 3D asset contained in the file \c testModel.fbx with \c balsam
the following command would be used:
 
\code
balsam testModel.fbx
\endcode
 
This would generate the following files:
\list
  \li \c meshes/testModel.mesh
  \li \c TestModel.qml
\endlist
 
Which can then be used in a Qt Quick 3D project by using that QML Component:
\code
import QtQuick3D
 
TestModel {
   id: modelInstance
}
\endcode
 
\note The generated mesh filename depends on the mesh name(s) defined in the
source file (in this example, the FBX file) and may differ from
\c{testModel.mesh}.
 
\section1 Balsam UI
 
There is also a GUI frontend for Balsam called \c balsamui that is shipped
alongside the \c balsam executable. In \c balsamui you can select your input
files and output directory and the command-line options of the \c balsam
executable are mapped to interactive elements:
 
\image balsamui.webp "A screenshot of the Balsam UI application."
 
\section1 Supported 3D Asset Types
 
\list
  \li Wavefront (.obj)
  \li COLLADA (.dae)
  \li FBX (.fbx)
  \li STL (.stl)
  \li PLY (.ply)
  \li GLTF2 (.gltf, .glb)
\endlist
 
Some of the formats supported also allow for either embedding or referencing of
texture assets. These assets are also supported, provided Qt also has support
for them.
 
\section2 glTF 2.0 Import
 
glTF 2.0 assets (.gltf and .glb) are imported by a native importer built
directly on Qt, instead of going through the Assimp library like the other
formats. The native importer supports the core glTF 2.0 feature set,
including skinning, morph targets, animations with LINEAR, STEP, and
CUBICSPLINE interpolation (the latter baked at a rate controlled by the
\c{--animationSampleRate} option), sparse accessors, and quantized meshes,
as well as the following extensions:
 
\list
  \li KHR_materials_pbrSpecularGlossiness
  \li KHR_materials_unlit
  \li KHR_materials_clearcoat
  \li KHR_materials_transmission
  \li KHR_materials_volume
  \li KHR_materials_ior
  \li KHR_materials_emissive_strength
  \li KHR_materials_specular
  \li KHR_materials_sheen
  \li KHR_materials_anisotropy
  \li KHR_materials_iridescence
  \li KHR_materials_dispersion
  \li KHR_texture_transform
  \li KHR_lights_punctual
  \li KHR_mesh_quantization
  \li KHR_node_visibility
  \li EXT_texture_webp
  \li EXT_meshopt_compression
  \li EXT_mesh_gpu_instancing
\endlist
 
For assets using KHR_materials_variants the generated component contains
all variant materials, a \c materialVariant property for selecting the
active variant by name, and a read-only \c materialVariants property
listing the available names. Passing the \c{--materialVariant} option
instead bakes the named variant, so only its materials are part of the
output.
Assets using KHR_xmp_json_ld are accepted, but the metadata is not
imported. Assets requiring KHR_draco_mesh_compression or
KHR_texture_basisu are not supported and are rejected with an error
naming the extension.
 
An asset that lists an extension balsam does not convert still loads: the
extension is ignored and a warning is logged. Accepting an asset is
therefore not the same as applying every extension it names, and an asset
that requires an extension the parser understands but the converter does not
act on loads rather than failing.
 
Some Assimp-specific post-processing options (such as
\c{--preTransformVertices} and \c{--optimizeMeshes}) do not apply to the
native importer; glTF scene data is imported as authored. Identical
vertices are joined by default like before, controlled by
\c{--joinIdenticalVertices}.
 
Normal generation differs from the Assimp importer. \c{--generateNormals},
which asks Assimp for flat normals on every face, is not recognized: the
specification mandates flat shading for a mesh without normal data, and that
is what the native importer produces. \c{--generateSmoothNormals} computes
smooth normals for such meshes instead, and unlike with the Assimp importer
it defaults to off. A glTF asset lacking normals therefore comes out flat
shaded unless \c{--generateSmoothNormals} is given.
 
During the transition period the \c{QT_QUICK3D_DISABLE_NATIVE_GLTF}
environment variable can be set to route glTF assets through the Assimp
importer instead.
 
\section1 Baking for Image-Based Lighting
 
Balsam also supports generating a pre-filtered cubemap image from .hdr
files. Specifying a file with .hdr extension as the input results in generating
a file with the same name but with an extension of .ktx. The application can
then ship the resulting .ktx file and reference that from the \l Texture
associated with \l SceneEnvironment::lightProbe. This avoids the costly runtime
processing that is necessary for image-based lighting. See \l{Pre-generating IBL
cubemap} for more details.
 
\section1 Supported Options
 
The following table lists the command-line options recognized by \c balsam when
converting asset files:
 
\note For each boolean option it is possible to use \c{--disable-<option-name>}.
 
\table
\header \li Option \li Description
\row \li \c {--outputPath, -o <outputPath>} \li Sets the location to place the
generated file(s). Default is the current directory.
\row \li \c {--calculateTangentSpace} \li Calculates the tangents and
bitangents for the imported meshes.
\row \li \c {--joinIdenticalVertices} \li Identifies and joins identical vertex
 data sets within all imported meshes.
\row \li \c {--generateNormals} \li Generates normals for all faces of all
meshes.
\row \li \c {--generateSmoothNormals} \li Generates smooth normals for all
vertices in the mesh.
\row \li \c {--splitLargeMeshes} \li Splits large meshes into smaller
sub-meshes.
\row \li \c {--preTransformVertices} \li Removes the node graph and
pre-transforms all vertices with the local transformation matrices of
their nodes.
\row \li \c {--improveCacheLocality} \li Reorders triangles for better vertex
cache locality.
\row \li \c {--removeRedundantMaterials} \li Searches for
redundant/unreferenced materials and removes them.
\row \li \c {--fixInfacingNormals} \li Tries to determine which meshes have
normal vectors that are facing inwards and inverts them.
\row \li \c {--findDegenerates} \li This step searches all meshes for
degenerate primitives and converts them to proper lines or points.
\row \li \c {--findInvalidData} \li This step searches all meshes for invalid
data, such as zeroed normal vectors or invalid UV coords and removes/fixes
them. This is intended to get rid of some common exporter errors.
\row \li \c {--transformUVCoordinates} \li This step applies per-texture UV
transformations and bakes them into stand-alone texture coordinate channels.
\row \li \c {--findInstances} \li This step searches for duplicate meshes and
replaces them with references to the first mesh.
\row \li \c {--optimizeMeshes} \li A postprocessing step to reduce the number
of meshes.
\row \li \c {--optimizeGraph} \li A postprocessing step to optimize the scene
hierarchy.
\row \li \c {--useFloatJointIndices} \li Stores joint indices as floating point
numbers for GLES 2.0.
\row \li \c {--globalScale} \li This step will perform a global scale of the
model.
\row \li \c {--globalScaleValue <value>} \li Global Scale factor used by
\c --globalScale.
\row \li \c {--dropNormals} \li Drops normals for all faces of all meshes.
\row \li \c {--removeComponentNormals} \li Removes Normal component from
meshes.
\row \li \c {--removeComponentTangentsAndBitangents} \li Removes Tangents and
Bitangents components from meshes.
\row \li \c {--removeComponentColors} \li Removes any Color components from
meshes.
\row \li \c {--removeComponentUVs} \li Removes any UV components from meshes.
\row \li \c {--removeComponentBoneWeights} \li Removes any bone weights from
meshes.
\row \li \c {--removeComponentAnimations} \li Removes any animation components
from meshes.
\row \li \c {--removeComponentTextures} \li Removes any embedded texture
components from meshes.
\row \li \c {--fbxPreservePivots} \li Preserves extra pivot nodes created by
FBX assets (can create deep node hierarchies)
\row \li \c {--generateMipMaps} \li Force all imported texture components to
generate mip maps for mip map texture filtering
\row \li \c {--useBinaryKeyframes} \li Record keyframe data as binary files
 
\row \li \c {--generateLightmapUV} \li Perform lightmap UV unwrapping and
generate an additional UV channel for the meshes. This UV data is then used by
the \l{Lightmaps and Global Illumination}{lightmap baker and during run-time
lightmapping}.
 
\row \li \c {--generateMeshLevelsOfDetail} \li When possible create mesh Levels
of Detail by automatically simplifying the source mesh.
 
\row \li \c {--recalculateLodNormals} \li Calculate new normals when necessary
for Generated Mesh levels of detail.
 
\row \li \c {--recalculateLodNormalsMergeAngle <value>} \li Maximum angle in
degrees to consider for normal smoothing/merging when recalculating normals
for Generated Mesh levels of detail.
 
\row \li \c {--recalculateLodNormalsSplitAngle <value>} \li Maximum angle in
degrees to consider for normal spliting when recalculating normals for
Generated Mesh levels of detail.
 
\endtable
 
*/