3D

Live link with Blender

Work on a 3D scene in Blender and see every change in JOS as you make it, and the other way round. Lights, cameras and transforms you set in JOS appear in Blender. Undo works in both applications.

What you need

• Blender 4.2 or later. Tested with 4.2 and 5.2.
• The same computer: JOS and Blender must run on one machine. The link only accepts connections from this computer.

Setting up

1. In JOS: Edit > Preferences > Live link > Install in Blender. JOS copies its add-on into every Blender 4.2 or later on this computer and turns it on. It says which ones it found.
2. Restart Blender. It connects to JOS by itself, whenever both are running.

That's all. Blender's scene shows in JOS's 3D view: JOS adds a ReadUSD for it to the Scene. JOS's own objects show in Blender.

• Updates: when JOS updates, it also updates the add-on in Blender. Restart Blender to use the new one.
• The connection: JOS's status bar shows it, for example "Live link: Blender: shot, updated 14:32:05". Hover over it for details. In Blender, the JOS tab of the 3D view's sidebar (N) shows it too, with Connect to JOS and Disconnect.
• The port is 8790, in Edit > Preferences > Live link and in the add-on's preferences. Change both if another program uses it.
• Several Blender files: each file is its own scene in JOS, with its own ReadUSD (named after the file: "Blender_shot"). live stage on the ReadUSD says which file it listens to.

What goes from Blender to JOS

• Objects:
• Meshes (with modifiers applied), curves, surfaces, metaballs and text, sent as meshes.
• Cameras, lights and empties, with their transforms and viewport visibility.
• Cameras: focal length, sensor, shift and clipping.
• Lights: point and spot become sphere lights, sun becomes distant, area becomes rect or disk. The brightness is approximate.
• Materials: as OpenPBR, with their textures; procedural parts are baked.
• Deleted and renamed objects are removed in JOS.

Each change is one undo step in JOS, "Live link: Blender". Changes made within a second are merged into one step.

Animation

• Send animation (checkbox): while you scrub in Blender, the current frame's values are sent as they change.
• Bake to JOS: sends the whole frame range in one go, as one undo step, and turns on Send animation. Its options:
• Bake deforming meshes: sends per-frame points for meshes that deform.
• Selected only
• Bake limit (MB): refuses bakes larger than this.

Blender's frame numbers line up with JOS's, shifted by the ReadUSD's time offset.

What goes from JOS to Blender

• JOS's objects (New): everything else in the Scene: other ReadUSDs' files (a set, a Kitchen Set), cubes, spheres, cards and VDBs made in JOS. They appear in Blender's JOS Objects collection, where JOS shows them. A change in JOS brings them in again: files apart from shapes, so moving a cube doesn't reload a whole set. Cards come without their picture.
• Moving JOS's things in Blender (New): move or turn a JOS light, camera, cube, sphere or card in Blender, and its node in JOS follows: its translate, rotate and scale are set, as one undo step. A light or camera can't be scaled, and a knob keyed in JOS is left as it is: Blender's status says so. A camera's lens or a light's power changed in Blender stays in Blender.
• Moves: moves you give the file's prims (in the 3D view or the Outliner) and the move of the group holding the ReadUSD move the Blender objects they apply to.
• Light3Ds and Camera3Ds: the lights in the ReadUSD's Scene, and the cameras of the RenderScenes rendering it, appear in Blender as objects named "JOS" plus the node's name (e.g. "JOS Light1") in a JOS collection.
• Animation: animated transforms, lights and cameras become keyframes in Blender, in an action group named "JOS". Turn this off in Preferences > Live link > Send JOS's animation. An object Blender already animates isn't keyed.

Undo, clearing and resending

• Undo: undo and redo in JOS also update Blender.
• Clear live edits (button on the ReadUSD): forgets everything received over the link. Ctrl+Z brings it back. Your files are never changed. Beside the button, JOS shows how much it has received ("live edits: 17.5 MB"); when that's a whole scene you didn't mean to send, clearing it makes the project small again.
• Resend all (Blender's JOS tab): sends the whole scene again, for example after Clear live edits.
• File > New or Open in JOS: Blender sends its scene again by itself into a new project, or into a project that has its ReadUSD. Another project (a 2D comp) is left alone.
• Losing the connection: if the connection drops, the add-on reconnects by itself. Opening another .blend file starts a new session under that file's name.
• Errors: any errors are listed in the add-on's panel.

In the Outliner and on export

• Outliner: prims that exist only through the live link are shown in italics.
• WriteUSD: writes what the link sent into the exported file.

Not yet

• Normals and instancing (instances go as separate meshes).
• Blender's world as a dome light.
• Animated light and material values from Blender.
• JOS's objects keyed in JOS move in Blender only when something changes in JOS, not frame by frame.
• Cards' pictures in Blender.
• Other applications: the link is for Blender only for now.