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diff --git a/modules/fbx/README.md b/modules/fbx/README.md deleted file mode 100644 index 8eca4bd3c9..0000000000 --- a/modules/fbx/README.md +++ /dev/null @@ -1,196 +0,0 @@ -# Open Source FBX Specification for the Importer - -The goal of this document is to make everything in FBX clearly stated, any errors will be corrected over time this -is a first draft. - -## fbx parser - originally from assimp - -- Folder: /modules/fbx/fbx_parser -- Upstream: assimp -- Original Version: git (308db73d0b3c2d1870cd3e465eaa283692a4cf23, 2019) -- License: BSD-3-Clause - -This can never be updated from upstream, we have heavily modified the parser to provide memory safety and add some -functionality. If anything we should give this parser back to assimp at some point as it has a lot of new features. - -# Updating assimp fbx parser - -Don't. It's not possible the code is rewritten in many areas to remove thirdparty deps and various bugs are fixed. - -Many days were put into rewriting the parser to use safe code and safe memory accessors. - -# File Headers - -FBX Binaries start with the header "Kaydara FBX Binary" - -FBX ASCII documents contain a larger header, sometimes with copyright information for a file. - -Detecting these is pretty simple. - -# What is an OP link? -It's an object to property link. It lists the properties for that object in some cases. Source and destination based by -ID. - -# What is a OO link? -Its an object to object link, it contains the ID source and destination ID. - -# FBX Node connections - -Nodes in FBX are connected using OO links, This means Object to Object. - -FBX has a single other kind of link which is Object Property, this is used for Object to Property Links, this can be - extra attributes, defaults, or even some simple settings. - -# Bones / Joints / Locators - -Bones in FBX are nodes, they initially have the Model:: Type, then have links to SubDeformer the sub deformer -is part of the skin there is also an explicit Skin link, which then links to the geometry using OO links in the -document. - -# Rotation Order in FBX compared to Godot - -**Godot uses the rotation order:** YXZ - -**FBX has dynamic rotation order to prevent gimbal lock with complex animations** - -```cpp -enum RotOrder { - RotOrder_EulerXYZ = 0 - RotOrder_EulerXZY, - RotOrder_EulerYZX, - RotOrder_EulerYXZ, - RotOrder_EulerZXY, - RotOrder_EulerZYX, - RotOrder_SphericXYZ // nobody uses this - as far as we can tell -}; -``` - - -# Pivot transforms - -### Pivot description: -- Maya and 3DS max consider everything to be in node space (bones joints, skins, lights, cameras, etc) -- Everything is a node, this means essentially nodes are auto or variants -- They are local to the node in the tree. -- They are used to calculate where a node is in space -```c++ -// For a better reference you can check editor_scene_importer_fbx.h -// references: GenFBXTransform / read the data in -// references: ComputePivotTransform / run the calculation -// This is the local pivot transform for the node, not the global transforms -Transform ComputePivotTransform( - Transform3D chain[TransformationComp_MAXIMUM], - Transform3D &geometric_transform) { - // Maya pivots - Transform3D T = chain[TransformationComp_Translation]; - Transform3D Roff = chain[TransformationComp_RotationOffset]; - Transform3D Rp = chain[TransformationComp_RotationPivot]; - Transform3D Rpre = chain[TransformationComp_PreRotation]; - Transform3D R = chain[TransformationComp_Rotation]; - Transform3D Rpost = chain[TransformationComp_PostRotation]; - Transform3D Soff = chain[TransformationComp_ScalingOffset]; - Transform3D Sp = chain[TransformationComp_ScalingPivot]; - Transform3D S = chain[TransformationComp_Scaling]; - - // 3DS Max Pivots - Transform3D OT = chain[TransformationComp_GeometricTranslation]; - Transform3D OR = chain[TransformationComp_GeometricRotation]; - Transform3D OS = chain[TransformationComp_GeometricScaling]; - - // Calculate 3DS max pivot transform - use geometric space (e.g doesn't effect children nodes only the current node) - geometric_transform = OT * OR * OS; - // Calculate standard maya pivots - return T * Roff * Rp * Rpre * R * Rpost.inverse() * Rp.inverse() * Soff * Sp * S * Sp.inverse(); -} -``` - -# Transform inheritance for FBX Nodes - -The goal of below is to explain why they implement this in the first place. - -The use case is to make nodes have an option to override their local scaling or to make scaling influenced by orientation, which i would imagine would be useful for when you need to rotate a node and the child to scale based on the orientation rather than setting on the rotation matrix planes. -```cpp -// not modified the formatting here since this code must remain clear -enum TransformInheritance { - Transform_RrSs = 0, - // Parent Rotation * Local Rotation * Parent Scale * Local Scale -- Parent Rotation Offset * Parent ScalingOffset (Local scaling is offset by rotation of parent node) - Transform_RSrs = 1, // Parent Rotation * Parent Scale * Local Rotation * Local Scale -- Parent * Local (normal mode) - Transform_Rrs = 2, // Parent Rotation * Local Rotation * Local Scale -- Node transform scale is the only relevant component - TransformInheritance_MAX // end-of-enum sentinel -}; - -enum TransformInheritance { - Transform_RrSs = 0, - // Local scaling is offset by rotation of parent node - Transform_RSrs = 1, - // Parent * Local (normal mode) - Transform_Rrs = 2, - // Node transform scale is the only relevant component - TransformInheritance_MAX // end-of-enum sentinel -}; -``` - -# Axis in FBX - -Godot has one format for the declared axis - -AXIS X, AXIS Y, -AXIS Z - -FBX supports any format you can think of. As it has to support Maya and 3DS Max. - -#### FBX File Header -```json -GlobalSettings: { - Version: 1000 - Properties70: { - P: "UpAxis", "int", "Integer", "",1 - P: "UpAxisSign", "int", "Integer", "",1 - P: "FrontAxis", "int", "Integer", "",2 - P: "FrontAxisSign", "int", "Integer", "",1 - P: "CoordAxis", "int", "Integer", "",0 - P: "CoordAxisSign", "int", "Integer", "",1 - P: "OriginalUpAxis", "int", "Integer", "",1 - P: "OriginalUpAxisSign", "int", "Integer", "",1 - P: "UnitScaleFactor", "double", "Number", "",1 - P: "OriginalUnitScaleFactor", "double", "Number", "",1 - P: "AmbientColor", "ColorRGB", "Color", "",0,0,0 - P: "DefaultCamera", "KString", "", "", "Producer Perspective" - P: "TimeMode", "enum", "", "",6 - P: "TimeProtocol", "enum", "", "",2 - P: "SnapOnFrameMode", "enum", "", "",0 - P: "TimeSpanStart", "KTime", "Time", "",0 - P: "TimeSpanStop", "KTime", "Time", "",92372316000 - P: "CustomFrameRate", "double", "Number", "",-1 - P: "TimeMarker", "Compound", "", "" - P: "CurrentTimeMarker", "int", "Integer", "",-1 - } -} -``` - -#### FBX FILE declares axis dynamically using FBX header -Coord is X -Up is Y -Front is Z - -#### GODOT - constant reference point -Coord is X positive, -Y is up positive, -Front is -Z negative - -### Explaining MeshGeometry indexing - -Reference type declared: -- Direct (directly related to the mapping information type) -- IndexToDirect (Map with key value, meaning depends on the MappingInformationType) - -ControlPoint is a vertex -* None The mapping is undetermined. -* ByVertex There will be one mapping coordinate for each surface control point/vertex. - * If you have direct reference type vertices [x] - * If you have IndexToDirect reference type the UV -* ByPolygonVertex There will be one mapping coordinate for each vertex, for every polygon of which it is a part. This means that a vertex will have as many mapping coordinates as polygons of which it is a part. (Sorted by polygon, referencing vertex) -* ByPolygon There can be only one mapping coordinate for the whole polygon. - * One mapping per polygon polygon x has this normal x - * For each vertex of the polygon then set the normal to x -* ByEdge There will be one mapping coordinate for each unique edge in the mesh. This is meant to be used with smoothing layer elements. (Mapping is referencing the edge id) -* AllSame There can be only one mapping coordinate for the whole surface. |