Alembic Out POP

Summary

The Alembic Out POP writes POP contents to an Alembic .abc file. It outputs points, vertices, and primitives similarly but not identically to the POPs structure. .abc files can contain multi-frame animations and built in and custom attributes. Multiple POPs can be input as separate objects within one Alembic file.

Each Alembic Out POP's Input requires exactly one of the following POPs primitive types to be present.

• Points are written as OPoints.
• Triangle and Quad primitives are written as OPolyMesh.
• Line Strips and Lines are written as OCurves with curve type set to Linear.

Where OPoints, OPolyMesh, and OCurves are the underlying objects passed to the Alembic SDK.

Note - each input POP must contain a single primitive type (i.e. an input POP can have only Triangles or only Point Primitives, however not both).

TouchDesigner converts Line Strip data to a set of points and list of lengths as Alembic's OCurves does not support vertex index references like they do for Triangles and Quads when exported to OPolyMesh. This means closed line strips are written out with a repeated starting vertex indicating its closed. (i.e. a closed line strip 0,1,2,3,0 will become an open line strip 0,1,2,3,4 where 0 and 4 are the same point). The Alembic In POP detects when the initial and final points are repeated and converts it into a closed line strip.

Output of Attributes:

• Point primitives support writing all Point attributes
• Triangle and Quad primitives support writing all Point, Vertex and Primitive attributes
• Lines and Line Strips support writing builtin Point and Primitive attributes. (see below for built in attributes)

Vertex List: Alembic uses a reversed winding order for primitives compared to TouchDesigner, this means the vertex order for each primitive is flipped when writing as well as when reading from the Alembic In POP.

Built in Attributes: Alembic Out POP will automatically export the following built in attributes

• Color attribute written as Cd float4
• N attribute written as N float3
• Tex attribute written as either uv float2 or when Export 3D Texture Coord is toggled as uv float3

Note - Line Strips and Lines only support built-in attributes for Point and Primitive attributes and does not support custom attribute writing.

For animated point clouds specifying the point attributes Point Id and Velocity writes these attributes as follows.

• Point Ids as .pointIds int64
• Velocity as .velocities float3

These attributes can be created from nodes such as Particle POP that create PartId and PartVel or as a custom attribute.

Custom Attribute data types: Point, Triangle, and Quad primitive support the following custom attribute types

• uint, int, float, double
• int2, float2, double2
• int3, float3, double3
• Array attributes

Output of POP groups: Alembic Out POP ignores POP groups.

Animated multi-frame output: The Topology Unchanged toggle can be enabled when an animated object does not have changing topologies, this will cause the topology to be written out once at the beginning.

Outputting multiple POPs to one Alembic file: Alembic Out POP supports exporting multiple POPs into a single Alembic file each as it's own individual object, under the root. For example writing two POPs will result in objects with paths /object1 and /object2.

See also Alembic, Alembic In POP, File Out POP

alembicoutPOP_Class

Parameters - Inputs Page

Input input - Start of Sequential Parameter Blocks managing the inputs of the POP.

In POP input0pop - Input POP for the current sequence block.

Object Name input0objname - Alembic object name.

Ids Attribute input0idname - Point attribute name containing point id information. Only available when exporting Point primtives.

Velocity Attribute input0velname - Point attribute name containing velocity information. Only available when exporting Point primtives.

Point Attribute Name input0ptattrname - Select with pattern matching which custom point attributes to save.

Vertex Attribute Name input0vertattrname - Select with pattern matching which custom vertex attributes to save.

Prim Attribute Name input0primattrname - Select with pattern matching which custom primitive attributes to save.

Parameters - Alembic Out Page

Unique Suffix uniquesuff - ⊞ - When enabled, me.fileSuffix will be a unique suffix when used in the file parameter.

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N n - N is the index used in me.fileSuffix. When unique suffix is enabled, N specifies the starting index to increment from when calculating a unique suffix/name.

Leading Zeros Digits leadingzerosdigits - Specify the minimum number of suffix digits that the filename will have. If the index number is less than this number, leading zeros will be appended to total the number of suffix digits to be this value.

File file - Sets the path and filename of the movie file that is saved out. The filename must include the file extension such as .obj/.exr etc.

FPS fps - The frame rate of the Alembic file created.

Limit Length limitlength - This can be used to automatically stop recording the file once it reaches a specified length.

Length length - ⊞ - The length to stop recording the file at.

• Length length -

• Length Unit lengthunit - Help Not Available.

Record record - When this parameter is set to 1, the file will be recording.

Record Pulse recordpulse - Instantly write out a file.

Pause pause - Pauses the recording.

Add Frame addframe - Adds a single frame to the output for each click of the button. Pause must be On to enable the Add Frame parameter.

Max Active Saves maxactive - Specifies the maximum number of file saving tasks can be running at once.

Include Primitives includeprim - This can be used to enable writing primtive data to the file.

Tex Coord Attribute texcoordattrib - When writing out to geometry files including texture coordinates, the name of the texture attribute to use (doesn't have to be Tex).

Topology Unchanged unchangedtopology - When writing can be used to indicate the topology will be unchanging, this will mean the topology will only be written once.

Samples per Second abcfps - Specify the time sampling rate provided to the Alembic library

Export 3D Texture Coord abc3dtex - When toggled textures will be written to a custom attrib with 3D textures, as Alembic supports 2D textures by default.

Parameters - Common Page

Bypass bypass - Pass through the first input to the output unchanged.

Free Extra GPU Memory freeextragpumem - Free memory that has accumulated when output memory has grown and shrunk.

Delete Input Attributes delinputattrs - Only output which attributes you specify in this POP - helps isolate attributes into a separate branch.

Operator Inputs

• Input 0: -

Info CHOP Channels

Extra Information for the Box POP can be accessed via an Info CHOP.

Common Operator Info Channels

• total_cooks - Number of times the operator has cooked since the process started.

• cook_time - Duration of the last cook in milliseconds.

• cook_frame - Frame number when this operator was last cooked relative to the component timeline.

• cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.

• cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.

• cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.

• cooked_this_frame - 1 if operator was cooked this frame.

• warnings - Number of warnings in this operator if any.

• errors - Number of errors in this operator if any.

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POPs (Point Operators) is a new Operator Family that works with 3D geometry or any general numeric data, runs on GPU-accelerated graphics cards or chips, is rendered as images or passed to devices like DMX lighting, LED arrays, lasers or other external systems.

Each SOP has a list of Points. Each point has an XYZ 3D position value plus other optional attributes. Each polygon Primitive is defined by a vertex list, which is list of point numbers.

A sequence of vertices form a Polygon in a SOP. Each vertex is an integer index into the Point List, and each Point holds an XYZ position and attributes like Normals and Texture Coordinates.

A surface type in POPs and SOPs that includes polygon, curve (NURBS and Bezier), patch (NURBS and Bezier) and other basic shapes like sphere, tube and metaball. Points and Primitives are part of the Geometry Detail, which is a part of a SOP.

Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.

Attributes make up the numeric data blocks of POPs. Each POPs has three blocks of data: a Point List which includes the P point Position attribute, a Primitive List and a Vertex List, and each are made of any number of attributes.

The Frames-per-Second that TouchDesigner's Timeline runs at. Set with project.cookRate.

To "pulse" a parameter is to send it a signal from (1) an exported CHOP channel or (2) a python command or (3) a mouse click that causes a new action to occur immediately. A pulse via python is via the .pulse() function on a pulse-type parameter, such as Reset parameter in a Speed CHOP. A pulse from a CHOP is typically a 0 to 1 to 0 signal in an exported channel.

The term "Frame" is a measurement of time used (1) in the Timeline, (2) as a time-unit in CHOPs, and (3) as a time unit in movie files that are read into TOPs and written out from TOPs. The frame rate is the frames per second (FPS).

An operator whose Bypass flag is set does nothing: All data going into its first input appears at its output unaffected.

The Graphics Processing Unit. This is the high-speed, many-core processor of the graphics card/chip that takes geometry, images and data from the CPU and creates images and processed data.

An Operator Family which operate on Channels (a sequence of numbers (Samples)) which are used for animation, audio, mathematics, simulation, logic, UI construction, and data streamed from/to devices and protocols.