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Alembic Mesh 3D Node

At times, you may need to import 3D geometry from applications like Blender, Cinema4D, or Maya. One of the formats you can use for importing 3D geometry is the Alembic file format. This file type is a 3D scene interchange format that contains baked animation with its geometry. In other words, it eliminates the animation calculation times by embedding fixed, uneditable animation with 3D geometry. The animation is typically embedded using a point cache, which saves the dynamic data such as velocity after it has been calculated. Alembic objects can contain mesh geometry, cameras, points, UVs, normals, and baked animation.

You can import Alembic files (.abc) into Fusion in two ways:

  • Choose File > Import > Alembic Scene in Fusion or Fusion > Import > Alembic Scene in DaVinci Resolveā€™s Fusion page.
  • Add an AlembicMesh3D node to the Node Editor.

The first method is the preferred method; both Alembic and FBX nodes by themselves import the entire model as one object. However, the Import menu breaks down the model, lights, camera, and animation into a string of individual nodes. This makes it easy to edit and modify and use subsections of the imported Alembic mesh. Also, transforms in the file are read into Fusion splines and into the Transform 3D nodes, which get saved with the comp. Later, when reloading the comp, the transforms are loaded from the comp and not the Alembic file. Fusion handles the meshes differently, always reloading them from the Alembic file.

Arbitrary user data varies depending on the software creating the Alembic file, and therefore this type of metadata is mostly ignored.

Alembic Import Dialog

An Alembic Import dialog is displayed once you select the file to import.

The top half of the Import dialog displays information about the selected file including the name of the plug-in/application that created the Alembic file, the version of the Alembic software developer kit used during the export, the duration of the animation in seconds, if available, and the frame rate(s) in the file.

Various objects and attributes can be imported by selecting the checkboxes in the Import section.

  • Hierarchy: When enabled, the full parenting hierarchy is recreated in Fusion using multiple Transform 3D nodes. When disabled, the transforms in the Alembic file are flattened down into the cameras and meshes. The flattening results in several meshes/cameras connected to a single Merge node in Fusion. It is best to have this disabled when the file includes animation. If enabled, the many rigs used to move objects in a scene will result in an equally large number of nodes in Fusion, so flattening will reduce the number of nodes in your node tree.
  • Orphaned Transforms: When the hierarchy option is enabled, an Orphaned Transforms setting is displayed. Activating this Orphan Transforms setting imports transforms that parent a mesh or camera. For example, if you have a skeleton and associated mesh model, the model is imported as an Alembic mesh, and the skeleton as a node tree of Merge3Ds. If this is disabled, the Merge3Ds are not created.
  • Cameras: When enabled, importing a file includes cameras along with Aperture, Angles of View, Plane of Focus, as well as Near and Far clipping plane settings. The resolution Gate Fit may be imported depending on whether the application used to export the file correctly tagged the resolution Gate Fit metadata. If your camera does not import successfully, check the setting for the Camera3D Resolution Gate Fit. Note that 3D Stereoscopic information is not imported.
  • InverseTransform: Imports the Inverse Transform (World to Model) for cameras.
  • Points: Alembic files support a Points type. This is a collection of 3D points with position information. Some 3D software exports particles as points. However, keep in mind that while position is included, the direction and orientation of the particles are lost.
  • Meshes: This setting determines whether importing includes 3D models from the Alembic file. If it is enabled, options to include UVs and normals are displayed.

Animation
This section includes one option for the Resampling rate. When exporting an Alembic animation, it is saved to disk using frames per second (fps). When importing Alembic data into Fusion, the fps are detected and entered into the Resample Rate field unless you have changed it previously in the current comp. Ideally, you should maintain the exported frame rate as the resample rate, so your samples match up with the original. The Detected Sampling Rates information at the top of the dialog can give an idea of what to pick if you are unsure. However, using this field, you can change the frame rate to create effects like slow motion.

Not all objects and properties in a 3D scene have an agreed upon universal convention in the Alembic file format. That being the case, Lights, Materials, Curves, Multiple UVs, and Velocities are not currently supported when you import Alembic files.

Since the FBX file format does support materials and lights, we recommend the use of FBX for lights, cameras, and materials. Use Alembic for meshes only

Alembic Mesh 3D Node Inputs

The AlembicMesh3D node has two inputs in the Node Editor. Both are optional since the node is designed to use the imported mesh.

  • SceneInput: The orange input can be used to connect an additional 3D scene or model. The imported Alembic objects combine with the other 3D geometry.
  • MaterialInput: The optional green input is used to apply a material to the geometry by connecting a 2D bitmap image. It applies the connected image to the surface of the geometry in the scene.

Alembic Mesh 3D Node Setup

The AlembicMesh3D node is designed to be part of a larger 3D scene. Typically, when imported, a 3D geometry model is represented by one node, and any transforms are in another node. The nodes imported as part of the Alembic file connect into a Merge 3D node along with a camera, lights, and other elements that may be required for the scene.

Alembic Mesh 3D Node Controls Tab

The first tab in the Inspector is the Controls tab. It includes a series of unique controls specific to the Alembic Mesh 3D node as well as six groupings of controls that are common to most 3D nodes.

Below are descriptions of the Alembic Mesh 3D specific controls.

  • Filename
    The complete file path of the imported Alembic file is displayed here. This field allows you to change or update the file linked to this node.
  • Object Name
    This text field shows the name of the imported Alembic mesh, which is also used to rename the Alembic Mesh 3D node in the Node Editor.

    When importing with the Alembic Mesh 3D node, if this text field is blank, the entire contents of the Alembic geometry are imported as a single mesh. When importing geometry using File > Import > Alembic Scene, this field is set by Fusion.
  • Wireframe
    Enabling this option causes the mesh to display only the wireframe for the object in the viewer. When enabled, there is a second option for wireframe anti-aliasing. You can also render these wireframes out to a file if the Renderer 3D node has the OpenGL render type selected.

Alembic Mesh 3D Node Controls, Materials, Transform, and Settings Tabs

The controls for Visibility, Lighting, Matte, Blend Mode, Normals/Tangents, and Object ID in the Controls tab are common in many 3D nodes. The Materials tab, Transforms tab and Settings tab in the Inspector are also duplicated in other 3D nodes.

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About the Author

Justin Robinson is a Certified DaVinci Resolve, Fusion & Fairlight instructor who is known for simplifying concepts and techniques for anyone looking to learn any aspect of the video post-production workflow. Justin is the founder of JayAreTV, a training and premade asset website offering affordable and accessible video post-production education. You can follow Justin on Twitter at @JayAreTV YouTube at JayAreTV or Facebook at MrJayAreTV

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