The goal of cast is to create an easy to use format for models, animations, materials, and game worlds. In addition, cast should be able to produce the same scenes in any 3d software.

• Autodesk Maya (2016+): Releases
• Blender (3.6+): Releases

• Python: Libraries/Python
• .NET Framework (by Scobalula): Cast.NET

• CastModelViewer (By echo000): Github

• SECast, a lossless converter to cast: SECast
• Note: If your tool supports exporting to cast directly, that is always better.

• Frequently asked questions: FAQ

All files are in little endian byte order and start with a cast header:

struct CastHeader
{
	uint32_t Magic;			// char[4] cast	(0x74736163)
	uint32_t Version;		// 0x1
	uint32_t RootNodes;		// Number of root nodes, which contain various sub nodes if necessary
	uint32_t Flags;			// Reserved for flags, or padding, whichever is needed
};

A cast file is basically a group of generic nodes. Nodes are given a unique registered id, which can tell the loader what the data is, and how to handle it.

Following the cast header is a collection of nodes which must be of type CastId::Root.

A node looks like:

struct CastNodeHeader
{
	CastId Identifier;		// Used to signify which class this node uses
	uint32_t NodeSize;		// Size of all data and sub data following the node
	uint64_t NodeHash;		// Unique hash, like an id, used to link nodes together
	uint32_t PropertyCount;	// The count of properties
	uint32_t ChildCount;	// The count of direct children nodes

	// We must read until the node size hits, and that means we are done.
	// The nodes are in a stack layout, so it's easy to load, FILO order.
};

There are several registered cast ids available:

enum class CastId : uint32_t
{
	Root = 0x746F6F72,
	Model = 0x6C646F6D,
	Mesh = 0x6873656D,
	Hair = 0x72696168,
	BlendShape = 0x68736C62,
	Skeleton = 0x6C656B73,
	Bone = 0x656E6F62,
	IKHandle = 0x64686B69,
	Constraint = 0x74736E63,
	Animation = 0x6D696E61,
	Curve = 0x76727563,
	CurveModeOverride = 0x564F4D43,
	NotificationTrack = 0x6669746E,
	Material = 0x6C74616D,
	File = 0x656C6966,
	Color = 0x726C6F63,
	Instance = 0x74736E69,
	Metadata = 0x6174656D,
};

Following a node, is the list of properties [Node.PropertyCount], a property looks like:

struct CastPropertyHeader
{
	CastPropertyId Identifier;	// The element type of this property
	uint16_t NameSize;			// The size of the name of this property
	uint32_t ArrayLength;		// The number of elements this property contains (1 for single)

	// Following is UTF-8 string lowercase, size of namesize, NOT null terminated
	// cast_property[ArrayLength] array of data
};

For properties, cast has several built in types:

enum class CastPropertyId : uint16_t
{
	Byte = 'b',			// <uint8_t>
	Short = 'h',		// <uint16_t>
	Integer32 = 'i',	// <uint32_t>
	Integer64 = 'l',	// <uint64_t>

	Float = 'f',		// <float>
	Double = 'd',		// <double>

	String = 's',		// Null terminated UTF-8 string

	Vector2 = 'v2',		// Float precision vector XY
	Vector3 = 'v3',		// Float precision vector XYZ
	Vector4 = 'v4'		// Float precision vector XYZW
};

To read a cast file, you just need to traverse the root nodes and their children. Properties always come before a nodes children. Each node has the total size of itself, and all children, so if a processor doesn't understand a node id, it can skip the entire node and continue reading.

Cast ids are stored as integers to make it faster to serialize and deserialize.

Notes:

• A root node represents a scene in a cast file.
• A root node may have 0-n of any of it's children nodes.
• All of a root nodes children must have unique hashes.

Notes:

• A model may have at most one skeleton node.
• A model may have 0-n of the other children nodes.
• The Position, Rotation, and Scale properties modify the model and it's children in world space.
  • Instance nodes should be preferred for large scene building.

Notes:

• Face Buffer is an index into the current meshes vertex data buffers where (0, 1, 2) are the first three vertices from this mesh.
• The Face Buffer follows CCW (right-handed) winding order, this may be different in other apis, where you may have to remap the indices.
• If a face contains an invalid index combination (0, 1, 1), (0, 1, 0), (0, 0, 0) where two or more indices are the same, it is acceptable for the user processing these faces to ignore them in order to properly render the mesh. It would be wise to present the user with a warning stating that this happened.
• Each vertex descriptor buffer must contain the same number of elements ex: if you have 16 vertices, you must have 16 normals if they exist, 16 colors if the buffer exists. Otherwise it's assumed they are default / skipped.
• Weights are additive which means having the same bone with 0.5 and 0.5 would end up making that bones influence 1.0 for example.
• The default skinning method is linear. When set to quaternion dual quaternion skinning is used.
• NEW 8/18/2024: The vertex color specification has changed, in order to support multiple color layers, a new Color Layer Count (cl) was added which mimics the UV Layer Count (ul) property.
  • To be backwards compatible, cast processors should check for cl, and use that by default along with the new c%d layer properties.
  • If the cl property does not exist, a processor should check for the legacy vc property which is the one and only color layer if it exists.
• NEW 4/21/2025: The vertex color buffer specification now allows supplying unpacked floating point rgba colors.

Notes:

• The Particle Buffer stores the particles in order by each strand, in world space.
• For each strand, there is a count in Segments Buffer, there is count + 1 particles for each strand.
  • A segment is the connection between two particles.
  • The sequence 1 -> 2 -> 3 is two segments 1 -> 2, 2 -> 3.

Notes:

• The Base Shape must be an existing cast mesh.
• The Target Shape Vertex Indices and Target Shape Vertex Positions must be the same length as they are paired together.
• Target Shape Vertex Positions is the final value of each changed vertex position ignoring the Base Shape's corresponding vertex.
• Target Weight Scale indicates the maximum value the target shape can deform to and should default to 1.0.

Notes:

• Segment Scale Compensate should default to True when not specified.
• Scale is always local to the current bone.

Notes:

• Use Target Rotation should default to False when not specified.
• Pole Bone must only effect the twist of the chain, in general you either have a Pole Bone or a Pole Vector Bone.

Notes:

• The constraint type values correspond to:
  • pt Point Constraint, which applies to translations.
  • or Orient Constraint, which applies to rotations.
  • sc Scale Constraint, which applies to scales.
• Maintain offset should default to False when not specified.
• Custom offset should match the following for the constraint types:
  • pt: Vector 3, default: [0.0, 0.0, 0.0].
  • or: Vector 4, default: [0.0, 0.0, 0.0, 1.0].
  • sc: Vector 3, default: [1.0, 1.0, 1.0].
• Skip X, Skip Y, and Skip Z should default to False when not specified and refer to ignoring that axis in the constraint.

Notes:

• The hash properties link to children of the material which can be:
  • A File which points to a texture.
  • A Color which has a single rgba value.

Notes:

• The Color Space property should default to srgb when not specified.

Notes:

• All curve keyframes are in object/node space.
• The Mode determines how each curve keyframe is applied to the node.
  • additive: The keyframe is added to the current scene frame value of the nodes property.
  • absolute: The keyframe is the exact value for the given frame.
  • relative: The keyframe is added to the rest position value of the nodes property.
• The property values correspond to:
  • rq Rotation Quaternion and expects v4 values.
  • tx Translation 'X' and expects f values.
  • ty Translation 'Y' and expects f values.
  • tz Translation 'Z' and expects f values.
  • sx Scale 'X' and expects f values.
  • sy Scale 'Y' and expects f values.
  • sz Scale 'Z' and expects f values.
  • bs BlendShape Weight and expects f values.
  • vb Visibility and expects b, h, or i values.
    • =0 = hidden.
    • >=1 = visible.
• The properties tx, ty, tz, sx, sy, sz, bs, vb should interpolate linearly.
• The property rq should interpolate with quaternion slerp.

Notes:

• See Curve notes above for the definition of each Mode value.
• Override Translation Curves should default to False when not specified.
• Override Rotation Curves should default to False when not specified.
• Override Scale Curves should default to False when not specified.
• The override node and all of it's children should override their curves mode to the new mode.
• The override node must be present at the time of processing in order to determine if a child bone is a descendent.

Notes:

• Author and Software are just for tagging cast files and have no use outside of metadata.
• Up Axis can be used as a hint to software to adjust the scene to match a specific up axis.
• Scene Root can be used as a root directory for resolving instance and other path relative nodes.
• A cast file can have any number of meta nodes but properties designed for hinting should only use the first metadata node instance.

• Format designed by DTZxPorter with input from the community.
• Icons by Smashicons